Collybistin/APC-stimulated guanine nucleotide exchange factor pleckstrin homology (PH) domain; Collybistin (also called PEM2) is homologous to the Dbl proteins ASEF (also called ARHGEF4/RhoGEF4) and SPATA13 (Spermatogenesis-associated protein 13; also called ASEF2). It activates CDC42 specifically and not any other Rho-family GTPases. Collybistin consists of an SH3 domain, followed by a RhoGEF/DH and PH domain. In Dbl proteins, the DH and PH domains catalyze the exchange of GDP for GTP in Rho GTPases, allowing them to signal to downstream effectors. It induces submembrane clustering of the receptor-associated peripheral membrane protein gephyrin, which is thought to form a scaffold underneath the postsynaptic membrane linking receptors to the cytoskeleton. It also acts as a tumor suppressor that links adenomatous polyposis coli (APC) protein, a negative regulator of the Wnt signaling pathway and promotes the phosphorylation and degradation of beta-catenin, to Cdc42. Autoinhibition of collybistin is accomplished by the binding of its SH3 domain with both the RhoGEF and PH domains to block access of Cdc42 to the GTPase-binding site. Inactivation promotes cancer progression. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 350 LESIDKIARWQVSIVGWEGLDILDRSSELIHSGELTKITKqGKSQQRTFFLFDHQLVSCKKDLLRRDMLYYKGRLDMDEM 429
Cdd:cd01224    1 MENLEKLAAWQSTVEGWEGEDLSDRSSELIHSGELTKISA-GRAQERTFFLFDHQLVYCKKDLLRRKNYIYKGRIDTDNM 79

                         90       100       110       120       130
                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 557947968 430 ELVDLGDGRDKDCNLSVKNAFKLVSRTTDEVYLFCAKKQEDKARWLQACADERRRVQED 488
Cdd:cd01224   80 EIEDLPDGKDDESGVTVKNAWKIYNASKNKWYVLCAKSAEEKQRWLEAFAEEREKVEKD 138

Src homology 3 domain of APC-Stimulated guanine nucleotide Exchange Factor; ASEF, also called ARHGEF4, exists in an autoinhibited form and is activated upon binding of the tumor suppressor APC (adenomatous polyposis coli). GEFs activate small GTPases by exchanging bound GDP for free GTP. ASEF can activate Rac1 or Cdc42. Truncated ASEF, which is found in colorectal cancers, is constitutively active and has been shown to promote angiogenesis and cancer cell migration. ASEF contains a SH3 domain followed by RhoGEF (also called Dbl-homologous or DH) and Pleckstrin Homology (PH) domains. In its autoinhibited form, the SH3 domain of ASEF forms an extensive interface with the DH and PH domains, blocking the Rac binding site. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 557947968  56 GGEQLAINELISDGNVVCAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRLRV 127
Cdd:cd11973    2 GGEQLAINELISDGSVVCAEALWDHVTMDDQELGFKAGDVIEVMDATNKEWWWGRVLDSEGWFPASFVRLRV 73

Collybistin/APC-stimulated guanine nucleotide exchange factor pleckstrin homology (PH) domain; Collybistin (also called PEM2) is homologous to the Dbl proteins ASEF (also called ARHGEF4/RhoGEF4) and SPATA13 (Spermatogenesis-associated protein 13; also called ASEF2). It activates CDC42 specifically and not any other Rho-family GTPases. Collybistin consists of an SH3 domain, followed by a RhoGEF/DH and PH domain. In Dbl proteins, the DH and PH domains catalyze the exchange of GDP for GTP in Rho GTPases, allowing them to signal to downstream effectors. It induces submembrane clustering of the receptor-associated peripheral membrane protein gephyrin, which is thought to form a scaffold underneath the postsynaptic membrane linking receptors to the cytoskeleton. It also acts as a tumor suppressor that links adenomatous polyposis coli (APC) protein, a negative regulator of the Wnt signaling pathway and promotes the phosphorylation and degradation of beta-catenin, to Cdc42. Autoinhibition of collybistin is accomplished by the binding of its SH3 domain with both the RhoGEF and PH domains to block access of Cdc42 to the GTPase-binding site. Inactivation promotes cancer progression. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 350 LESIDKIARWQVSIVGWEGLDILDRSSELIHSGELTKITKqGKSQQRTFFLFDHQLVSCKKDLLRRDMLYYKGRLDMDEM 429
Cdd:cd01224    1 MENLEKLAAWQSTVEGWEGEDLSDRSSELIHSGELTKISA-GRAQERTFFLFDHQLVYCKKDLLRRKNYIYKGRIDTDNM 79

                         90       100       110       120       130
                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 557947968 430 ELVDLGDGRDKDCNLSVKNAFKLVSRTTDEVYLFCAKKQEDKARWLQACADERRRVQED 488
Cdd:cd01224   80 EIEDLPDGKDDESGVTVKNAWKIYNASKNKWYVLCAKSAEEKQRWLEAFAEEREKVEKD 138

Guanine nucleotide exchange factor for Rho/Rac/Cdc42-like GTPases; Also called Dbl-homologous (DH) domain. It appears that PH domains invariably occur C-terminal to RhoGEF/DH domains.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 163 RTNVIREIMDTERVYIKHLRDICEGYIRQCRKHTGMFTVAQLATIFGNIEDIYKFQRKFLKDLEKQYNKEEPHLSEIGSC 242
Cdd:cd00160    1 RQEVIKELLQTERNYVRDLKLLVEVFLKPLDKELLPLSPEEVELLFGNIEEIYEFHRIFLKSLEERVEEWDKSGPRIGDV 80

                         90       100       110       120       130       140       150       160
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 243 FLQNQEGFAIYSEYCNNHPGACLELANLMKQgkyRHFFEACRLLQQ--MIDIAIDGFLLTPVQKICKYPLQLAELLKYTT 320
Cdd:cd00160   81 FLKLAPFFKIYSEYCSNHPDALELLKKLKKF---NKFFQEFLEKAEseCGRLKLESLLLKPVQRLTKYPLLLKELLKHTP 157

                        170       180
                 ....*....|....*....|....
gi 557947968 321 QEHGDYSNIKAAYEAMKNVACLIN 344
Cdd:cd00160  158 DGHEDREDLKKALEAIKEVASQVN 181

Src homology 3 domain of APC-Stimulated guanine nucleotide Exchange Factor; ASEF, also called ARHGEF4, exists in an autoinhibited form and is activated upon binding of the tumor suppressor APC (adenomatous polyposis coli). GEFs activate small GTPases by exchanging bound GDP for free GTP. ASEF can activate Rac1 or Cdc42. Truncated ASEF, which is found in colorectal cancers, is constitutively active and has been shown to promote angiogenesis and cancer cell migration. ASEF contains a SH3 domain followed by RhoGEF (also called Dbl-homologous or DH) and Pleckstrin Homology (PH) domains. In its autoinhibited form, the SH3 domain of ASEF forms an extensive interface with the DH and PH domains, blocking the Rac binding site. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 557947968  56 GGEQLAINELISDGNVVCAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRLRV 127
Cdd:cd11973    2 GGEQLAINELISDGSVVCAEALWDHVTMDDQELGFKAGDVIEVMDATNKEWWWGRVLDSEGWFPASFVRLRV 73

Pleckstrin homology domain; Domain commonly found in eukaryotic signalling proteins. The domain family possesses multiple functions including the abilities to bind inositol phosphates, and various proteins. PH domains have been found to possess inserted domains (such as in PLC gamma, syntrophins) and to be inserted within other domains. Mutations in Brutons tyrosine kinase (Btk) within its PH domain cause X-linked agammaglobulinaemia (XLA) in patients. Point mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968   378 LIHSGELTKITKQGKS--QQRTFFLFDHQLVSCKKDLLRRDmLYYKGRLDMDEMELVDLGDGRDKDcnlsVKNAFKLVSR 455
Cdd:smart00233   1 VIKEGWLYKKSGGGKKswKKRYFVLFNSTLLYYKSKKDKKS-YKPKGSIDLSGCTVREAPDPDSSK----KPHCFEIKTS 75

                           90       100
                   ....*....|....*....|..
gi 557947968   456 TtDEVYLFCAKKQEDKARWLQA 477
Cdd:smart00233  76 D-RKTLLLQAESEEEREKWVEA 96

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 557947968   76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRS-EDKEAWFPA 120
Cdd:pfam00018   2 ALYDYTAQEPDELSFKKGDIIIVLEKSEDGWWKGRNkGGKEGLIPS 47

Collybistin/APC-stimulated guanine nucleotide exchange factor pleckstrin homology (PH) domain; Collybistin (also called PEM2) is homologous to the Dbl proteins ASEF (also called ARHGEF4/RhoGEF4) and SPATA13 (Spermatogenesis-associated protein 13; also called ASEF2). It activates CDC42 specifically and not any other Rho-family GTPases. Collybistin consists of an SH3 domain, followed by a RhoGEF/DH and PH domain. In Dbl proteins, the DH and PH domains catalyze the exchange of GDP for GTP in Rho GTPases, allowing them to signal to downstream effectors. It induces submembrane clustering of the receptor-associated peripheral membrane protein gephyrin, which is thought to form a scaffold underneath the postsynaptic membrane linking receptors to the cytoskeleton. It also acts as a tumor suppressor that links adenomatous polyposis coli (APC) protein, a negative regulator of the Wnt signaling pathway and promotes the phosphorylation and degradation of beta-catenin, to Cdc42. Autoinhibition of collybistin is accomplished by the binding of its SH3 domain with both the RhoGEF and PH domains to block access of Cdc42 to the GTPase-binding site. Inactivation promotes cancer progression. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 350 LESIDKIARWQVSIVGWEGLDILDRSSELIHSGELTKITKqGKSQQRTFFLFDHQLVSCKKDLLRRDMLYYKGRLDMDEM 429
Cdd:cd01224    1 MENLEKLAAWQSTVEGWEGEDLSDRSSELIHSGELTKISA-GRAQERTFFLFDHQLVYCKKDLLRRKNYIYKGRIDTDNM 79

                         90       100       110       120       130
                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 557947968 430 ELVDLGDGRDKDCNLSVKNAFKLVSRTTDEVYLFCAKKQEDKARWLQACADERRRVQED 488
Cdd:cd01224   80 EIEDLPDGKDDESGVTVKNAWKIYNASKNKWYVLCAKSAEEKQRWLEAFAEEREKVEKD 138

Guanine nucleotide exchange factor for Rho/Rac/Cdc42-like GTPases; Also called Dbl-homologous (DH) domain. It appears that PH domains invariably occur C-terminal to RhoGEF/DH domains.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 163 RTNVIREIMDTERVYIKHLRDICEGYIRQCRKHTGMFTVAQLATIFGNIEDIYKFQRKFLKDLEKQYNKEEPHLSEIGSC 242
Cdd:cd00160    1 RQEVIKELLQTERNYVRDLKLLVEVFLKPLDKELLPLSPEEVELLFGNIEEIYEFHRIFLKSLEERVEEWDKSGPRIGDV 80

                         90       100       110       120       130       140       150       160
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 243 FLQNQEGFAIYSEYCNNHPGACLELANLMKQgkyRHFFEACRLLQQ--MIDIAIDGFLLTPVQKICKYPLQLAELLKYTT 320
Cdd:cd00160   81 FLKLAPFFKIYSEYCSNHPDALELLKKLKKF---NKFFQEFLEKAEseCGRLKLESLLLKPVQRLTKYPLLLKELLKHTP 157

                        170       180
                 ....*....|....*....|....
gi 557947968 321 QEHGDYSNIKAAYEAMKNVACLIN 344
Cdd:cd00160  158 DGHEDREDLKKALEAIKEVASQVN 181

Src homology 3 domain of APC-Stimulated guanine nucleotide Exchange Factor; ASEF, also called ARHGEF4, exists in an autoinhibited form and is activated upon binding of the tumor suppressor APC (adenomatous polyposis coli). GEFs activate small GTPases by exchanging bound GDP for free GTP. ASEF can activate Rac1 or Cdc42. Truncated ASEF, which is found in colorectal cancers, is constitutively active and has been shown to promote angiogenesis and cancer cell migration. ASEF contains a SH3 domain followed by RhoGEF (also called Dbl-homologous or DH) and Pleckstrin Homology (PH) domains. In its autoinhibited form, the SH3 domain of ASEF forms an extensive interface with the DH and PH domains, blocking the Rac binding site. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 557947968  56 GGEQLAINELISDGNVVCAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRLRV 127
Cdd:cd11973    2 GGEQLAINELISDGSVVCAEALWDHVTMDDQELGFKAGDVIEVMDATNKEWWWGRVLDSEGWFPASFVRLRV 73

Src homology 3 domain of ARHGEF9-like Rho guanine nucleotide exchange factors; Members of this family contain a SH3 domain followed by RhoGEF (also called Dbl-homologous or DH) and Pleckstrin Homology (PH) domains. They include the Rho guanine nucleotide exchange factors ARHGEF9, ASEF (also called ARHGEF4), ASEF2, and similar proteins. GEFs activate small GTPases by exchanging bound GDP for free GTP. ARHGEF9 specifically activates Cdc42, while both ASEF and ASEF2 can activate Rac1 and Cdc42. ARHGEF9 is highly expressed in the brain and it interacts with gephyrin, a postsynaptic protein associated with GABA and glycine receptors. ASEF plays a role in angiogenesis and cell migration. ASEF2 is important in cell migration and adhesion dynamics. ASEF exists in an autoinhibited form and is activated upon binding of the tumor suppressor APC (adenomatous polyposis coli), leading to the activation of Rac1 or Cdc42. In its autoinhibited form, the SH3 domain of ASEF forms an extensive interface with the DH and PH domains, blocking the Rac binding site. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 557947968  73 CAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd11828    1 LAEALWDHVTMDPEELGFKAGDVIEVLDMSDKDWWWGSIRDEEGWFPASFVRL 53

Src homology 3 domains; Src homology 3 (SH3) domains bind to target proteins through sequences containing proline and hydrophobic amino acids. Pro-containing polypeptides may bind to SH3 domains in 2 different binding orientations.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 557947968    74 AEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSED-KEAWFPASFVR 124
Cdd:smart00326   5 VRALYDYTAQDPDELSFKKGDIITVLEKSDDGWWKGRLGRgKEGLFPSNYVE 56

Pleckstrin homology domain; Domain commonly found in eukaryotic signalling proteins. The domain family possesses multiple functions including the abilities to bind inositol phosphates, and various proteins. PH domains have been found to possess inserted domains (such as in PLC gamma, syntrophins) and to be inserted within other domains. Mutations in Brutons tyrosine kinase (Btk) within its PH domain cause X-linked agammaglobulinaemia (XLA) in patients. Point mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968   378 LIHSGELTKITKQGKS--QQRTFFLFDHQLVSCKKDLLRRDmLYYKGRLDMDEMELVDLGDGRDKDcnlsVKNAFKLVSR 455
Cdd:smart00233   1 VIKEGWLYKKSGGGKKswKKRYFVLFNSTLLYYKSKKDKKS-YKPKGSIDLSGCTVREAPDPDSSK----KPHCFEIKTS 75

                           90       100
                   ....*....|....*....|..
gi 557947968   456 TtDEVYLFCAKKQEDKARWLQA 477
Cdd:smart00233  76 D-RKTLLLQAESEEEREKWVEA 96

Src homology 3 domains of the p47phox subunit of NADPH oxidase and similar domains; This family is composed of the tandem SH3 domains of p47phox subunit of NADPH oxidase and Nox Organizing protein 1 (NoxO1), the four SH3 domains of Tks4 (Tyr kinase substrate with four SH3 domains), the five SH3 domains of Tks5, the SH3 domain of obscurin, Myosin-I, and similar domains. Most members of this group also contain Phox homology (PX) domains, except for obscurin and Myosin-I. p47phox and NoxO1 are regulators of the phagocytic NADPH oxidase complex (also called Nox2 or gp91phox) and nonphagocytic NADPH oxidase Nox1, respectively. They play roles in the activation of their respective NADPH oxidase, which catalyzes the transfer of electrons from NADPH to molecular oxygen to form superoxide. Tks proteins are Src substrates and scaffolding proteins that play important roles in the formation of podosomes and invadopodia, the dynamic actin-rich structures that are related to cell migration and cancer cell invasion. Obscurin is a giant muscle protein that plays important roles in the organization and assembly of the myofibril and the sarcoplasmic reticulum. Type I myosins (Myosin-I) are actin-dependent motors in endocytic actin structures and actin patches. They play roles in membrane traffic in endocytic and secretory pathways, cell motility, and mechanosensing. Myosin-I contains an N-terminal actin-activated ATPase, a phospholipid-binding TH1 (tail homology 1) domain, and a C-terminal extension which includes an F-actin-binding TH2 domain, an SH3 domain, and an acidic peptide that participates in activating the Arp2/3complex. The SH3 domain of myosin-I is required for myosin-I-induced actin polymerization. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 557947968  75 EALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVR 124
Cdd:cd11856    3 VAIADYEAQGDDEISLQEGEVVEVLEKNDSGWWYVRKGDKEGWVPASYLE 52

C-terminal Src homology 3 domain of Growth factor receptor-bound protein 2 (GRB2) and related proteins; This family includes the adaptor protein GRB2 and related proteins including Drosophila melanogaster Downstream of receptor kinase (DRK), Caenorhabditis elegans Sex muscle abnormal protein 5 (Sem-5), GRB2-related adaptor protein (GRAP), GRAP2, and similar proteins. Family members contain an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. GRB2/Sem-5/DRK is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. GRAP2 plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. GRAP acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. The C-terminal SH3 domains (SH3c) of GRB2 and GRAP2 have been shown to bind to classical PxxP motif ligands, as well as to non-classical motifs. GRB2 SH3c binds Gab2 (Grb2-associated binder 2) through epitopes containing RxxK motifs, while the SH3c of GRAP2 binds to the phosphatase-like protein HD-PTP via a RxxxxK motif. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11805    2 VQALYDFNPQEPGELEFRRGDIITVLDSSDPDWWKGELRGRVGIFPANYV 51

Src homology 3 domain of Signal Transducing Adaptor Molecules; STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. There are two vertebrate STAMs, STAM1 and STAM2, which may be functionally redundant; vertebrate STAMs contain ITAM motifs. They are part of the endosomal sorting complex required for transport (ESCRT-0). STAM2 deficiency in mice did not cause any obvious abnormality, while STAM1 deficiency resulted in growth retardation. Loss of both STAM1 and STAM2 in mice proved lethal, indicating that STAMs are important for embryonic development. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11820    5 ALYDFEAAEDNELTFKAGEIITVLDDSDPNWWKGSNHRGEGLFPANFV 52

Son of Sevenless (SOS) Pleckstrin homology (PH) domain; SOS is a Ras guanine nucleotide exchange factor. SOS is thought to transmit signals from activated receptor tyrosine kinases to the Ras signaling pathway. SOS contains a histone domain, Dbl-homology (DH), a PH domain, Rem domain, Cdc25 domain, and a Grb2 binding domain. The SOS PH domain binds to phosphatidylinositol-4,5-bisphosphate (PIP2) and phosphatidic acid (PA). SOS is dependent on Ras binding to the allosteric site via its histone domain for both a lower level of activity (Ras GDP) and maximal activity (Ras GTP). The DH domain blocks the allosteric Ras binding site in SOS. The PH domain is closely associated with the DH domain and the action of the DH-PH unit gates a reciprocal interaction between Ras and SOS. The C-terminal proline-rich domain of SOS binds to the adapter protein Grb2 which localizes the Sos protein to the plasma membrane and diminishes the negative effect of the C-terminal domain on the guanine nucleotide exchange activity of the CDC25-homology domain of SOS. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 375 SSELIHSGELTKITKQGKSQQRTFFLFDHQLVSCKKDLLRR------DMLYYKGRLDMDEMELVDLGDGRDkdcnlsVKN 448
Cdd:cd01261    3 CNEFIMEGTLGKVGSGKRKTERHAFLFDGLLLLCKSNRRRTstggpkPEYRLKEKFFIRKVEINDLEDTEE------LKN 76

                         90       100
                 ....*....|....*....|....*....
gi 557947968 449 AFKLVSRTTDEVYLFCaKKQEDKARWLQA 477
Cdd:cd01261   77 AFEIVPRDQPSVILFA-KSAEEKNNWMAA 104

Src homology 3 domain of Signal Transducing Adaptor Molecule 1; STAM1 is part of the endosomal sorting complex required for transport (ESCRT-0) and is involved in sorting ubiquitinated cargo proteins from the endosome. It may also be involved in the regulation of IL2 and GM-CSF mediated signaling, and has been implicated in neural cell survival. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11964    5 AIYDFEAAEDNELTFKAGDIITILDDSDPNWWKGETPQGTGLFPSNFV 52

Src homology 3 domain of Protein arginine N-methyltransferase 2; PRMT2, also called HRMT1L1, belongs to the arginine methyltransferase protein family. It functions as a coactivator to both estrogen receptor alpha (ER-alpha) and androgen receptor (AR), presumably through arginine methylation. The ER-alpha transcription factor is involved in cell proliferation, differentiation, morphogenesis, and apoptosis, and is also implicated in the development and progression of breast cancer. PRMT2 and its variants are upregulated in breast cancer cells and may be involved in modulating the ER-alpha signaling pathway during formation of breast cancer. PRMT2 also plays a role in regulating the function of E2F transcription factors, which are critical cell cycle regulators, by binding to the retinoblastoma gene product (RB). It contains an N-terminal SH3 domain and an AdoMet binding domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11806    4 AIADFVATDDSQLSFESGDKLLVLRKPSVDWWWAEHNGCCGYIPASHL 51

Src homology 3 domain of Signal Transducing Adaptor Molecule 2; STAM2, also called EAST (Epidermal growth factor receptor-associated protein with SH3 and TAM domain) or Hbp (Hrs binding protein), is part of the endosomal sorting complex required for transport (ESCRT-0). It plays a role in sorting mono-ubiquinated endosomal cargo for trafficking to the lysosome for degradation. It is also involved in the regulation of exocytosis. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11963    6 ALYDFEAVEDNELTFKHGEIIIVLDDSDANWWKGENHRGVGLFPSNFV 53

Src Homology 3 (SH3) domain of Apoptosis Stimulating of p53 protein 2; ASPP2 is the full length form of the previously-identified tumor supressor, p53-binding protein 2 (p53BP2). ASPP2 activates the apoptotic function of the p53 family of tumor suppressors (p53, p63, and p73). It plays a central role in regulating apoptosis and cell growth; ASPP2-deficient mice show postnatal death. Downregulated expression of ASPP2 is frequently found in breast tumors, lung cancer, and diffuse large B-cell lymphoma where it is correlated with a poor clinical outcome. ASPP2 contains a proline-rich region, four ankyrin (ANK) repeats, and an SH3 domain at its C-terminal half. The SH3 domain and the ANK repeats of ASPP2 contribute to the p53 binding site; they bind to the DNA binding domain of p53. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKD---WWWGRSEDKEAWFPASFVRL 125
Cdd:cd11953    5 ALWDYEGESDDELSFKEGDCMTILRREDEDeteWWWARLNDKEGYVPRNLLGL 57

Second Src homology 3 domain (or SH3B) of Intersectin; Intersectins (ITSNs) are adaptor proteins that function in exo- and endocytosis, actin cytoskeletal reorganization, and signal transduction. They are essential for initiating clathrin-coated pit formation. They bind to many proteins through their multidomain structure and facilitate the assembly of multimeric complexes. Vertebrates contain two ITSN proteins, ITSN1 and ITSN2, which exist in alternatively spliced short and long isoforms. The short isoforms contain two Eps15 homology domains (EH1 and EH2), a coiled-coil region and five SH3 domains (SH3A-E), while the long isoforms, in addition, contain RhoGEF (also called Dbl-homologous or DH), Pleckstrin homology (PH) and C2 domains. ITSN1 and ITSN2 are both widely expressed, with variations depending on tissue type and stage of development. The second SH3 domain (or SH3B) of ITSN1 has been shown to bind WNK and CdGAP. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|..
gi 557947968  85 DQELGFKAGDVIQVLEaSNKDWWWGRSED-KEAWFPASFVRL 125
Cdd:cd11837   13 ENHLSFAKGDIITVLE-QQEMWWFGELEGgEEGWFPKSYVKE 53

Src Homology 3 domain of the p40phox subunit of NADPH oxidase; p40phox, also called Neutrophil cytosol factor 4 (NCF-4), is a cytosolic subunit of the phagocytic NADPH oxidase complex (also called Nox2 or gp91phox) which plays a crucial role in the cellular response to bacterial infection. NADPH oxidase catalyzes the transfer of electrons from NADPH to oxygen during phagocytosis forming superoxide and reactive oxygen species. p40phox positively regulates NADPH oxidase in both phosphatidylinositol-3-phosphate (PI3P)-dependent and PI3P-independent manner. It contains an N-terminal PX domain, a central SH3 domain, and a C-terminal PB1 domain that interacts with p67phox. The SH3 domain of p40phox binds to canonical polyproline and noncanonical motifs at the C-terminus of p47phox. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd11869    2 AEALFDFTGNSKLELNFKAGDVIFLLSRVNKDWLEGTVRGATGIFPLSFVKI 53

Src homology 3 domain of Hematopoietic lineage cell-specific protein 1; HS1, also called HCLS1 (hematopoietic cell-specific Lyn substrate 1), is a cortactin homolog expressed specifically in hematopoietic cells. It is an actin regulatory protein that binds the Arp2/3 complex and stabilizes branched actin filaments. It is required for cell spreading and signaling in lymphocytes. It regulates cytoskeletal remodeling that controls lymphocyte trafficking, and it also affects tissue invasion and infiltration of leukemic B cells. Like cortactin, HS1 contains an N-terminal acidic domain, several copies of a repeat domain found in cortactin and HS1, a proline-rich region, and a C-terminal SH3 domain. The N-terminal region binds the Arp2/3 complex and F-actin, while the C-terminal region acts as an adaptor or scaffold that can connect varied proteins that bind the SH3 domain within the actin network. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....
gi 557947968  72 VCAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd12073    1 ICAVALYDYQGEGDDEISFDPQETITDIEMVDEGWWKGTCHGHRGLFPANYVEL 54

Src homology 3 domain of Src kinase-like Protein Tyrosine Kinases; Src subfamily members include Src, Lck, Hck, Blk, Lyn, Fgr, Fyn, Yrk, Yes, and Brk. Src (or c-Src) proteins are cytoplasmic (or non-receptor) PTKs which are anchored to the plasma membrane. They contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Brk lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. They were identified as the first proto-oncogene products, and they regulate cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Src kinases are overexpressed in a variety of human cancers, making them attractive targets for therapy. They are also implicated in acute inflammatory responses and osteoclast function. Src, Fyn, Yes, and Yrk are widely expressed, while Blk, Lck, Hck, Fgr, Lyn, and Brk show a limited expression pattern. This subfamily also includes Drosophila Src42A, Src oncogene at 42A (also known as Dsrc41) which accumulates at sites of cell-cell or cell-matrix adhesion, and participates in Drosphila development and wound healing. It has been shown to promote tube elongation in the tracheal system, is essential for proper cell-cell matching during dorsal closure, and regulates cell-cell contacts in developing Drosophila eyes. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*....
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSED--KEAWFPASF 122
Cdd:cd11845    4 ALYDYEARTDDDLSFKKGDRLQILDDSDGDWWLARHLStgKEGYIPSNY 52

Pleckstrin homology domain-containing family G members 1, 2, and 3 pleckstrin homology (PH) domain; PLEKHG1 (also called ARHGEF41), PLEKHG2 (also called ARHGEF42 or CLG/common-site lymphoma/leukemia guanine nucleotide exchange factor2), and PLEKHG3 (also called ARHGEF43) have RhoGEF DH/double-homology domains in tandem with a PH domain which is involved in phospholipid binding. They function as a guanine nucleotide exchange factor (GEF) and are involved in the regulation of Rho protein signal transduction. Mutations in PLEKHG1 have been associated panic disorder (PD), an anxiety disorder characterized by panic attacks and anticipatory anxiety. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 326 YSNIKAAYEAMKNVACLINERKRKLESIDKIARWQVSIVGWEGLDILDRSSELIHSGeltkITKQGKSQQRTFFLFDHQL 405
Cdd:cd13243    1 RSVVEEALDTMTQVAWHINDMKRKHEHAVRVQEIQSLLDGWEGPELTTYGDLVLEGT----FRMAGAKNERLLFLFDKML 76

                         90       100       110       120       130       140       150
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 557947968 406 VSCKKdllRRDMLY-YKGRLDMDEMELVDLGDGRdkdcnlsvKNAFKLVSRTTDEV-YLFCAKKQEDKARWLQ 476
Cdd:cd13243   77 LITKK---REDGILqYKTHIMCSNLMLSESIPKE--------PLSFQVLPFDNPKLqYTLQAKNQEQKRLWTQ 138

Pleckstrin homology (PH) domain; PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 557947968 380 HSGELTKITKQGKS--QQRTFFLFDHQLVSCKKDllRRDMLYYKGRLDMDEMELVDLGDGRDKdcnlsvKNAFKLVSRTt 457
Cdd:cd00821    1 KEGYLLKRGGGGLKswKKRWFVLFEGVLLYYKSK--KDSSYKPKGSIPLSGILEVEEVSPKER------PHCFELVTPD- 71

                         90       100
                 ....*....|....*....|.
gi 557947968 458 DEVYLFCAKKQEDKARWLQAC 478
Cdd:cd00821   72 GRTYYLQADSEEERQEWLKAL 92

Src Homology 3 domain of metazoan osteoclast stimulating factor 1; OSTF1, also named OSF or SH3P2, is a signaling protein containing SH3 and ankyrin-repeat domains. It acts through a Src-related pathway to enhance the formation of osteoclasts and bone resorption. It also acts as a negative regulator of cell motility. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11772    4 ALYDYEAQHPDELSFEEGDLLYISDKSDPNWWKATCGGKTGLIPSNYV 51

Second Src homology 3 domain (or SH3B) of Intersectin-2; Intersectin-2 (ITSN2) is an adaptor protein that functions in exo- and endocytosis, actin cytoskeletal reorganization, and signal transduction. It plays a role in clathrin-coated pit (CCP) formation. It binds to many proteins through its multidomain structure and facilitate the assembly of multimeric complexes. ITSN2 also functions as a specific GEF for Cdc42 activation in epithelial morphogenesis, and is required in mitotic spindle orientation. It exists in alternatively spliced short and long isoforms. The short isoform contains two Eps15 homology domains (EH1 and EH2), a coiled-coil region and five SH3 domains (SH3A-E), while the long isoform, in addition, contains RhoGEF (also called Dbl-homologous or DH), Pleckstrin homology (PH) and C2 domains. The second SH3 domain (or SH3B) of ITSN2 is expected to bind protein partners, similar to ITSN1 which has been shown to bind WNK and CdGAP. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEaSNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd11990    2 AQALCSWTAKKDNHLNFSKNDIITVLE-QQENWWFGEVHGGRGWFPKSYVKL 52

Src homology 3 domain of Alpha Spectrin; Spectrin is a major structural component of the red blood cell membrane skeleton and is important in erythropoiesis and membrane biogenesis. It is a flexible, rope-like molecule composed of two subunits, alpha and beta, which consist of many spectrin-type repeats. Alpha and beta spectrin associate to form heterodimers and tetramers; spectrin tetramer formation is critical for red cell shape and deformability. Defects in alpha spectrin have been associated with inherited hemolytic anemias including hereditary spherocytosis (HSp), hereditary elliptocytosis (HE), and hereditary pyropoikilocytosis (HPP). Alpha spectrin contains a middle SH3 domain and a C-terminal EF-hand binding motif in addition to multiple spectrin repeats. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 557947968  73 CAEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVR 124
Cdd:cd11808    1 CVVALYDYQEKSPREVSMKKGDILTLLNSSNKDWWKVEVNDRQGFVPAAYVK 52

Second C-terminal Src homology 3 domain of Fungal Actin-binding protein 1; Abp1 is an adaptor protein that functions in receptor-mediated endocytosis and vesicle trafficking. It contains an N-terminal actin-binding module, the actin-depolymerizing factor (ADF) homology domain, a central proline-rich region, and a C-terminal SH3 domain (many yeast Abp1 proteins contain two C-terminal SH3 domains). Yeast Abp1 also contains two acidic domains that bind directly to the Arp2/3 complex, which is required to initiate actin polymerization. The SH3 domain of yeast Abp1 binds and localizes the kinases, Ark1p and Prk1p, which facilitate actin patch disassembly following vesicle internalization. It also mediates the localization to the actin patch of the synaptojanin-like protein, Sjl2p, which plays a key role in endocytosis. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd11961    2 AKALYDYDAAEDNELSFFENDKIINIEFVDDDWWLGECHGSRGLFPSNYVEL 53

Variant SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|
gi 557947968   76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:pfam07653   4 VIFDYVGTDKNGLTLKKGDVVKVLGKDNDGWWEGETGGRVGLVPSTAVEE 53

Fifth Src homology 3 domain (or SH3E) of Intersectin-1; Intersectin-1 (ITSN1) is an adaptor protein that functions in exo- and endocytosis, actin cytoskeletal reorganization, and signal transduction. It plays a role in clathrin-coated pit (CCP) formation. It binds to many proteins through its multidomain structure and facilitate the assembly of multimeric complexes. ITSN1 localizes in membranous organelles, CCPs, the Golgi complex, and may be involved in the cell membrane trafficking system. It exists in alternatively spliced short and long isoforms. The short isoform contains two Eps15 homology domains (EH1 and EH2), a coiled-coil region and five SH3 domains (SH3A-E), while the long isoform, in addition, contains RhoGEF (also called Dbl-homologous or DH), Pleckstrin homology (PH) and C2 domains. The fifth SH3 domain (or SH3E) of ITSN1 has been shown to bind many protein partners including SGIP1, Sos1, dynamin1/2, CIN85, c-Cbl, SHIP2, N-WASP, and synaptojanin-1, among others. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 557947968  76 ALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFVRL 125
Cdd:cd11995    5 GMYDYTAQNDDELAFSKGQIINVLNKEDPDWWKGELNGQVGLFPSNYVKL 54

Third N-terminal Src homology 3 domain of Dynamin Binding Protein, also called Tuba; DNMBP or Tuba is a cdc42-specific guanine nucleotide exchange factor (GEF) that contains four N-terminal SH3 domains, a central RhoGEF [or Dbl homology (DH)] domain followed by a Bin/Amphiphysin/Rvs (BAR) domain, and two C-terminal SH3 domains. It provides a functional link between dynamin and key regulatory proteins of the actin cytoskeleton. It plays an important role in regulating cell junction configuration. The four N-terminal SH3 domains of DNMBP binds the GTPase dynamin, which plays an important role in the fission of endocytic vesicles. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEASNKDWWWGRSEDKEAWFPASFV 123
Cdd:cd11796    2 ARVLQDLSAQLDEELDLREGDVVTITGILDKGWFRGELNGRRGIFPEGFV 51

Src Homology 3 domain of SH3 domain-containing protein 21 (SH3D21) and similar proteins; N-terminal SH3 domain of the uncharacterized protein SH3 domain-containing protein 21, and similar uncharacterized domains, it belongs to the CD2AP-like_3 subfamily of proteins. The CD2AP-like_3 subfamily is composed of the third SH3 domain (SH3C) of CD2AP, CIN85 (Cbl-interacting protein of 85 kDa), and similar domains. CD2AP and CIN85 are adaptor proteins that bind to protein partners and assemble complexes that have been implicated in T cell activation, kidney function, and apoptosis of neuronal cells. They also associate with endocytic proteins, actin cytoskeleton components, and other adaptor proteins involved in receptor tyrosine kinase (RTK) signaling. CD2AP and the main isoform of CIN85 contain three SH3 domains, a proline-rich region, and a C-terminal coiled-coil domain. All of these domains enable CD2AP and CIN85 to bind various protein partners and assemble complexes that have been implicated in many different functions. SH3C of both proteins have been shown to bind to ubiquitin. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 557947968  73 CAEALWDHVTMDDQELGFKAGDVIQVLEASNKD--WWWGRSEDKEAWFPASFV 123
Cdd:cd12142    1 YCRVLFDYNPVAPDELALKKGDVIEVISKETEDegWWEGELNGRRGFFPDNFV 53

Src homology 3 domain of SH3 domain containing Ysc84-like 1 (SH3YL1) protein; SH3YL1 localizes to the plasma membrane and is required for dorsal ruffle formation. It binds phosphoinositides (PIs) with high affinity through its N-terminal SYLF domain (also called DUF500). In addition, SH3YL1 contains a C-terminal SH3 domain which has been reported to bind to N-WASP, dynamin 2, and SHIP2 (a PI 5-phosphatase). SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|..
gi 557947968  74 AEALWDHVTMDDQELGFKAGDVIQVLEASNK--DWWWGRSEDKEAWFPASFV 123
Cdd:cd11841    2 VTALYSFEGQQPCDLSFQAGDRITVLTRTDSqfDWWEGRLRGRVGIFPANYV 53