Fibronectin type 3 domain; One of three types of internal repeats found in the plasma protein fibronectin. Its tenth fibronectin type III repeat contains an RGD cell recognition sequence in a flexible loop between 2 strands. Approximately 2% of all animal proteins contain the FN3 repeat; including extracellular and intracellular proteins, membrane spanning cytokine receptors, growth hormone receptors, tyrosine phosphatase receptors, and adhesion molecules. FN3-like domains are also found in bacterial glycosyl hydrolases.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087 116 PGPPAApLEIKGLTAEKCYLSWGPPQENGGaEIDHYIVEKRETSRLAWTLCEAELPT-TSCKVTKLLRGNEYIFRVMGVN 194
Cdd:cd00063     1 PSPPTN-LRVTDVTSTSVTLSWTPPEDDGG-PITGYVVEYREKGSGDWKEVEVTPGSeTSYTLTGLKPGTEYEFRVRAVN 78

                          90
                  ....*....|....
gi 1111814087 195 KYGVGEPLESDAVK 208
Cdd:cd00063    79 GGGESPPSESVTVT 92

Fibronectin type 3 domain; One of three types of internal repeats found in the plasma protein fibronectin. Its tenth fibronectin type III repeat contains an RGD cell recognition sequence in a flexible loop between 2 strands. Approximately 2% of all animal proteins contain the FN3 repeat; including extracellular and intracellular proteins, membrane spanning cytokine receptors, growth hormone receptors, tyrosine phosphatase receptors, and adhesion molecules. FN3-like domains are also found in bacterial glycosyl hydrolases.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087 116 PGPPAApLEIKGLTAEKCYLSWGPPQENGGaEIDHYIVEKRETSRLAWTLCEAELPT-TSCKVTKLLRGNEYIFRVMGVN 194
Cdd:cd00063     1 PSPPTN-LRVTDVTSTSVTLSWTPPEDDGG-PITGYVVEYREKGSGDWKEVEVTPGSeTSYTLTGLKPGTEYEFRVRAVN 78

                          90
                  ....*....|....
gi 1111814087 195 KYGVGEPLESDAVK 208
Cdd:cd00063    79 GGGESPPSESVTVT 92

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  32 VVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAVNCK 111
Cdd:pfam07679  10 VEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGKYTCVATNSAGEAEASAELT 89

                  .
gi 1111814087 112 V 112
Cdd:pfam07679  90 V 90

Fibronectin type III domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087 118 PPAAPLEIKGLTAEKCYLSWGPPqENGGAEIDHYIVEKRETSRL-AWTLCEAELPTTSCKVTKLLRGNEYIFRVMGVNKY 196
Cdd:pfam00041   1 SAPSNLTVTDVTSTSLTVSWTPP-PDGNGPITGYEVEYRPKNSGePWNEITVPGTTTSVTLTGLKPGTEYEVRVQAVNGG 79

                  ....*
gi 1111814087 197 GVGEP 201
Cdd:pfam00041  80 GEGPP 84

Fibronectin type 3 domain [General function prediction only];

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....
gi 1111814087 183 GNEYIFRVMGVNKYGVGEPleSDAVKALDPFTAPSPPLNLEITSVTKESMTLCW 236
Cdd:COG3401   202 GTTYYYRVAATDTGGESAP--SNEVSVTTPTTPPSAPTGLTATADTPGSVTLSW 253

Fibronectin type 3 domain; One of three types of internal repeats found in the plasma protein fibronectin. Its tenth fibronectin type III repeat contains an RGD cell recognition sequence in a flexible loop between 2 strands. Approximately 2% of all animal proteins contain the FN3 repeat; including extracellular and intracellular proteins, membrane spanning cytokine receptors, growth hormone receptors, tyrosine phosphatase receptors, and adhesion molecules. FN3-like domains are also found in bacterial glycosyl hydrolases.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087 116 PGPPAApLEIKGLTAEKCYLSWGPPQENGGaEIDHYIVEKRETSRLAWTLCEAELPT-TSCKVTKLLRGNEYIFRVMGVN 194
Cdd:cd00063     1 PSPPTN-LRVTDVTSTSVTLSWTPPEDDGG-PITGYVVEYREKGSGDWKEVEVTPGSeTSYTLTGLKPGTEYEFRVRAVN 78

                          90
                  ....*....|....
gi 1111814087 195 KYGVGEPLESDAVK 208
Cdd:cd00063    79 GGGESPPSESVTVT 92

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  32 VVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAVNCK 111
Cdd:pfam07679  10 VEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGTYTLTISNVQPDDSGKYTCVATNSAGEAEASAELT 89

                  .
gi 1111814087 112 V 112
Cdd:pfam07679  90 V 90

Eighth immunoglobulin (Ig)-like domain of human myosin light-chain kinase (MLCK) and similar protein; member of the I-set of IgSF domains; The members here are composed of the eighth immunoglobulin (Ig)-like domain of human myosin light-chain kinase (MLCK) and similar proteins. Myosin light-chain kinase (MLCK) is a key regulator of different forms of cell motility involving actin and myosin II. Agonist stimulation of smooth muscle cells increases cytosolic Ca2+ which binds calmodulin. This Ca2+-calmodulin complex in turn binds to and activates MLCK. Activated MLCK leads to the phosphorylation of the 20 kDa myosin regulatory light chain (RLC) of myosin II and the stimulation of actin-activated myosin MgATPase activity. MLCK is widely present in vertebrate tissues; it phosphorylates the 20 kDa RLC of both smooth and nonmuscle myosin II. Phosphorylation leads to the activation of the myosin motor domain and altered structural properties of myosin II. In smooth muscle MLCK it is involved in initiating contraction. In nonmuscle cells, MLCK may participate in cell division and cell motility; it has been suggested MLCK plays a role in cardiomyocyte differentiation and contraction through regulation of nonmuscle myosin II.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  20 PRImmdVKFRDVVVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQN 99
Cdd:cd05762     2 PQI---IQFPEDMKVRAGESVELFCKVTGTQPITCTWMKFRKQIQEGEGIKIENTENSSKLTITEGQQEHCGCYTLEVEN 78

                          90       100
                  ....*....|....*....|.
gi 1111814087 100 VAGTRSLAVNCKVLDRPGPPA 120
Cdd:cd05762    79 KLGSRQAQVNLTVVDKPDPPA 99

Fibronectin type 3 domain [General function prediction only];

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  93 YVLTLQNVAGTRSLAVN-CKVLDRPGPPAAP--LEIKGLTAEKCYLSWGPPQENGgaeIDHYIVEKRETSRLAWTLCEAE 169
Cdd:COG3401   300 YRVTAVDAAGNESAPSNvVSVTTDLTPPAAPsgLTATAVGSSSITLSWTASSDAD---VTGYNVYRSTSGGGTYTKIAET 376

                          90       100       110       120       130
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 1111814087 170 LPTTSCKVTKLLRGNEYIFRVMGVNKYGVgEPLESDAVKALDPFTAPSPPLNLEITSVT 228
Cdd:COG3401   377 VTTTSYTDTGLTPGTTYYYKVTAVDAAGN-ESAPSEEVSATTASAASGESLTASVDAVP 434

C5 immunoglobulin (Ig) domain of cardiac myosin binding protein C (MyBP-C); The members here are composed of the C5 immunoglobulin (Ig) domain of cardiac myosin binding protein C (MyBP-C). MyBP-C consists of repeated domains, Ig and fibronectin type 3, and various linkers. Three isoforms of MYBP-C exist: slow-skeletal (ssMyBP-C), fast-skeletal (fsMyBP-C), and cardiac (cMyBP-C). cMYBP-C has insertions between and inside domains and an additional cardiac-specific Ig domain at the N-terminus. For cMYBP_C an interaction has been demonstrated between this C5 domain and the Ig C8 domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  30 DVVVVKAGEILKINADIAGRPLPVISWTKDGKEIEE-KARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAV 108
Cdd:cd05894     3 NTIVVVAGNKLRLDVPISGEPAPTVTWSRGDKAFTAtEGRVRVESYKDLSSFVIEGAEREDEGVYTITVTNPVGEDHASL 82

                  ....
gi 1111814087 109 NCKV 112
Cdd:cd05894    83 FVKV 86

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087   31 VVVVKAGEILKINADIAGRPLPVISWTKDG-KEIEEKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAVN 109
Cdd:smart00410   3 SVTVKEGESVTLSCEASGSPPPEVTWYKQGgKLLAESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGTT 82

                   ...
gi 1111814087  110 CKV 112
Cdd:smart00410  83 LTV 85

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  46 IAGRPLPVISWTKDGKEIEEKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRS 105
Cdd:cd00096     7 ASGNPPPTITWYKNGKPLPPSSRDSRRSELGNGTLTISNVTLEDSGTYTCVASNSAGGSA 66

Third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule 1 (NCAM-1); member of the I-set of IgSF domains; The members here are composed of the third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1111814087  37 GEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDhTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAVNCKV 112
Cdd:cd05730    18 GQSVTLACDADGFPEPTMTWTKDGEPIESGEEKYSFNED-GSEMTILDVDKLDEAEYTCIAENKAGEQEAEIHLKV 92

Second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of the Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit-1,Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit-2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*...
gi 1111814087  48 GRPLPVISWTKDGKEIEEK-ARVEIVsTDHTTAITVKDciRRDSGQYVLTLQNVAGTR 104
Cdd:cd05724    24 GHPEPTVSWRKDGQPLNLDnERVRIV-DDGNLLIAEAR--KSDEGTYKCVATNMVGER 78

Immunoglobulin (Ig)-like domain of vascular endothelial growth factor receptor (VEGFR); member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain of vascular endothelial growth factor receptor (VEGFR). The VEGFRs have an extracellular component with seven Ig-like domains, a transmembrane segment, and an intracellular tyrosine kinase domain interrupted by a kinase-insert domain. The VEGFR family consists of three members, VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1), and VEGFR-3 (Flt-4). VEGFRs bind VEGFs with high affinity at the Ig-like domains. VEGF-A is important to the growth and maintenance of vascular endothelial cells and to the development of new blood- and lymphatic-vessels in physiological and pathological states. VEGFR-2 is a major mediator of the mitogenic, angiogenic, and microvascular permeability-enhancing effects of VEGF-A. VEGFR-1 may play an inhibitory part in these processes by binding VEGF and interfering with its interaction with VEGFR-2. VEGFR-1 has a signaling role in mediating monocyte chemotaxis. VEGFR-1 and VEGFR-2 may mediate a chemotactic and a survival signal in hematopoietic stem cells or leukemia cells. VEGFR-3 has been shown to be involved in tumor angiogenesis and growth. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  31 VVVVKAGEIL-KINADIAGRPLPVISWTKDGKEIEEKARVEivsTDHttAITVKDCIRRDSGQYVLTLQN 99
Cdd:cd04976    11 VLEATAGKRSvRLPMKVKAYPPPEVVWYKDGLPLTEKARYL---TRH--SLIIKEVTEEDTGNYTILLSN 75

Second C-terminal immunoglobulin (Ig)-like domain of palladin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of palladin. Palladin belongs to the palladin-myotilin-myopalladin family. Proteins belonging to this family contain multiple Ig-like domains and function as scaffolds, modulating actin cytoskeleton. Palladin binds to alpha-actinin ezrin, vasodilator-stimulated phosphoprotein VASP, SPIN90 (also known as DIP or mDia interacting protein), and Src. Palladin also binds F-actin directly, via its Ig3 domain. Palladin is expressed as several alternatively spliced isoforms, having various combinations of Ig-like domains, in a cell-type-specific manner. It has been suggested that palladin's different Ig-like domains may be specialized for distinct functions. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1111814087  32 VVVKAGEILKINADIAGRPLPVISWTKDGKEIE-EKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRSLAV 108
Cdd:cd20990    10 LTVQEGKLCRMDCKVSGLPTPDLSWQLDGKPIRpDSAHKMLVRENGVHSLIIEPVTSRDAGIYTCIATNRAGQNSFNL 87

Immunoglobulin (Ig)-like ectodomain of the LRIG1 (Leucine-rich Repeats And Immunoglobulin-like Domains Protein 1) and similar proteins; member of the I-set of IgSF domains; The members here are composed of subgroup of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. The ectodomain of LRIG1 has two distinct regions: the proposed 15 LRRs and three Ig-like domains closer to the membrane. LRIG1 has been reported to interact with many receptor tyrosine kinases, GDNF/c-Ret, E-cadherin, JAK/STAT, c-Met, and the EGFR family signaling systems. Immunoglobulin Superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The structure of the LRIG1 extracellular Ig domain lacks a C" strand and thus is better described as a member of the I-set of IgSF domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  32 VVVKAGEILKINADIAGRPLPVISWTKDGK---EIEEKARVEIVSTDHTTAITvkDCIRRDSGQYVLTLQNVAGTRSLAV 108
Cdd:cd05763     9 ITIRAGSTARLECAATGHPTPQIAWQKDGGtdfPAARERRMHVMPEDDVFFIV--DVKIEDTGVYSCTAQNSAGSISANA 86

                  ....*
gi 1111814087 109 NCKVL 113
Cdd:cd05763    87 TLTVL 91

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  30 DVVVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVsTDHTtaITVKDCIRRDSGQYVLTLQNVAGTRSLAVN 109
Cdd:cd20978     9 KNVVVKGGQDVTLPCQVTGVPQPKITWLHNGKPLQGPMERATV-EDGT--LTIINVQPEDTGYYGCVATNEIGDIYTETL 85

                  ...
gi 1111814087 110 CKV 112
Cdd:cd20978    86 LHV 88

Third immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the Constant 2 (C2)-set of IgSF domains; The members here are composed of the third immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C, and C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1111814087  31 VVVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDhttAITVKDCIRRDSGQY 93
Cdd:cd20957    10 VQTVDFGRTAVFNCSVTGNPIHTVLWMKDGKPLGHSSRVQILSED---VLVIPSVKREDKGMY 69

Third immunoglobulin-like domain of the human WFIKKN (WAP, follistatin, immunoglobulin, Kunitz and NTR domain-containing protein), and similar domains; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin-like domain of the human WFIKKN (WAP, follistatin, immunoglobulin, Kunitz and NTR domain-containing protein) and similar proteins. WFIKKN is a secreted protein that consists of multiple types of protease inhibitory modules, including two tandem Kunitz-type protease inhibitor-domains. The Ig superfamily is a heterogenous group of proteins built on a common fold comprised of a sandwich of two beta sheets. Members of the Ig superfamily are components of immunoglobulin, neuroglia, cell surface glycoproteins, such as T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, such as butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1111814087  34 VKAGEILKINADIAGRPLPVISWTkdgKEIEEKARVeIVSTDHTTAITVKDCIR---------RDSGQYVLTLQNVAG 102
Cdd:cd05765    12 VKVGETASFHCDVTGRPQPEITWE---KQVPGKENL-IMRPNHVRGNVVVTNIGqlviynaqpQDAGLYTCTARNSGG 85

Fourth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1111814087  47 AGRPLPVISWTKDGKEIEEKARV----------EIVSTDHTTAITVkdcirRDSGQYVLTLQNVAGT 103
Cdd:cd20956    26 SGNPLPQITWTLDGFPIPESPRFrvgdyvtsdgDVVSYVNISSVRV-----EDGGEYTCTATNDVGS 87

Immunoglobulin (Ig)-like domain of myotilin, palladin, and myopalladin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain in myotilin, palladin, and myopalladin. Myotilin, palladin, and myopalladin function as scaffolds that regulate actin organization. Myotilin and myopalladin are most abundant in skeletal and cardiac muscle; palladin is ubiquitously expressed in the organs of developing vertebrates and plays a key role in cellular morphogenesis. The three family members each interact with specific molecular partners with all three binding to alpha-actinin; In addition, palladin also binds to vasodilator-stimulated phosphoprotein (VASP) and ezrin, myotilin binds to filamin and actin, and myopalladin also binds to nebulin and cardiac ankyrin repeat protein (CARP). This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

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gi 1111814087  34 VKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIV---STDHTTAItvKDCIRRDSGQYVLTLQNVAG 102
Cdd:cd05744    12 VQEGRLCRFDCKVSGLPTPDLFWQLNGKPVRPDSAHKMLvreNGRHSLII--EPVTKRDAGIYTCIARNRAG 81

Immunoglobulin (Ig)-like domain of vascular endothelial growth factor receptor 2 (VEGFR-2); member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain of vascular endothelial growth factor receptor 2 (VEGFR-2). The VEGFRs have an extracellular component with seven Ig-like domains, a transmembrane segment, and an intracellular tyrosine kinase domain interrupted by a kinase-insert domain. VEGFRs bind VEGFs with high affinity at the Ig-like domains. VEGFR-2 (KDR/Flk-1) is a major mediator of the mitogenic, angiogenic and microvascular permeability-enhancing effects of VEGF-A; VEGF-A is important to the growth and maintenance of vascular endothelial cells and to the development of new blood- and lymphatic-vessels in physiological and pathological states. VEGF-A also interacts with VEGFR-1, which it binds more strongly than VEGFR-2. VEGFR-1 and VEGFR-2 may mediate a chemotactic and a survival signal in hematopoietic stem cells or leukemia cells. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1111814087  31 VVVVKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIvstdhTTAITVKDCIRRDSGQYVLTLQN 99
Cdd:cd05864    11 LVEAKVGERVRIPVKYLGYPPPEIKWYKNGIPIESNHTIKA-----GHVLTIMEVTEKDAGNYTVVLTN 74

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of slit responsiveness, antagonizes slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors

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gi 1111814087  32 VVVKAGEILKINADIAGRPLPVISWTKDGKEIeeKARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGTRS 105
Cdd:cd20952     9 QTVAVGGTVVLNCQATGEPVPTISWLKDGVPL--LGKDERITTLENGSLQIKGAEKSDTGEYTCVALNLSGEAT 80

Fifth immunoglobulin (Ig) domain of contactin; The members here are composed of the fifth immunoglobulin (Ig) domain of contactins. Contactins are neural cell adhesion molecules and are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. The first four Ig domains form the intermolecular binding fragment, which arranges as a compact U-shaped module via contacts between Ig domains 1 and 4, and between Ig domains 2 and 3. Contactin-2 (TAG-1, axonin-1) may play a part in the neuronal processes of neurite outgrowth, axon guidance and fasciculation, and neuronal migration. This group also includes contactin-1 and contactin-5. The different contactins show different expression patterns in the central nervous system. During development and in adulthood, contactin-2 is transiently expressed in subsets of central and peripheral neurons. Contactin-5 is expressed specifically in the rat postnatal nervous system, peaking at about 3 weeks postnatal, and a lack of contactin-5 (NB-2) results in an impairment of neuronal activity in the rat auditory system. Contactin-5 is highly expressed in the adult human brain in the occipital lobe and in the amygdala. Contactin-1 is differentially expressed in tumor tissues and may, through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma.

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gi 1111814087  29 RDVVVVKAGEILkINADIAGRPLPVISWTKDGKEIEEKARVEIVStDHTTAItvKDCIRRDSGQYVLTLQNVAGTRS 105
Cdd:cd04969    10 KKILAAKGGDVI-IECKPKASPKPTISWSKGTELLTNSSRICILP-DGSLKI--KNVTKSDEGKYTCFAVNFFGKAN 82

Third immunoglobulin (Ig)-like domain of peroxidasin; The members here are composed of the third immunoglobulin (Ig)-like domain in peroxidasin. Peroxidasin has a peroxidase domain and interacting extracellular motifs containing four Ig-like domains. It has been suggested that peroxidasin is secreted and has functions related to the stabilization of the extracellular matrix. It may play a part in various other important processes such as removal and destruction of cells which have undergone programmed cell death and protection of the organism against non-self.

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gi 1111814087  37 GEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDhttAITVKDCIRRDSGQYVLTLQNVAGTRSLAVNCKV 112
Cdd:cd05745     2 GQTVDFLCEAQGYPQPVIAWTKGGSQLSVDRRHLVLSSG---TLRISRVALHDQGQYECQAVNIVGSQRTVAQLTV 74

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three IG-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans.

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gi 1111814087  34 VKAGEILKINADIAGRPLPVISWTKDGKEIEEKARVEIVSTDHTT-AITVKDCIRRDSGQYVLTLQNVAGT 103
Cdd:cd05857    16 VPAANTVKFRCPAAGNPTPTMRWLKNGKEFKQEHRIGGYKVRNQHwSLIMESVVPSDKGNYTCVVENEYGS 86

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1111814087  37 GEILKINADIAGRPLPVISWTKDGKEIEekarveiVSTDHTTA------ITVKDCIRRDSGQYVLTLQNVAGTrslaVNC 110
Cdd:cd20976    16 GQDFVAQCSARGKPVPRITWIRNAQPLQ-------YAADRSTCeagvgeLHIQDVLPEDHGTYTCLAKNAAGQ----VSC 84

                  ..
gi 1111814087 111 KV 112
Cdd:cd20976    85 SA 86

Fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related); The members here are composed of the fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related). These proteins belong to the L1 subfamily of cell adhesion molecules (CAMs) and are comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. These molecules are primarily expressed in the nervous system. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth.

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gi 1111814087  33 VVKAGEILKINADIAGRPLPVISWTKDGKEIEEkARVEIVSTDHTTAITVKDCIRRDSGQYVLTLQNVAGT 103
Cdd:cd04978    10 VLSPGETGELICEAEGNPQPTITWRLNGVPIEP-APEDMRRTVDGRTLIFSNLQPNDTAVYQCNASNVHGY 79