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        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 253 KVGEVFTVDLGEAILFDCSADSHPPNTYSWIRR-------TDNTTYIIKHGPRLEVaSEKVAQKTMDYVCCAYNNITGRQ 325
Cdd:cd20969   7 RKAQQVFVDEGHTVQFVCRADGDPPPAILWLSPrkhlvsaKSNGRLTVFPDGTLEV-RYAQVQDNGTYLCIAANAGGNDS 85

                ....*..
gi 86439957 326 DETHFTV 332
Cdd:cd20969  86 MPAHLHV 92

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 157 SGAVEYVGNMTLTCHVEGgTRLAYQWLKNGRPVHTSSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRNPVSEMESDiimpi 236
Cdd:cd05740   9 SNPVEDKDAVTLTCEPET-QNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANRSD----- 82

                        90
                ....*....|.
gi 86439957 237 iyygPYGLQVN 247
Cdd:cd05740  83 ----PVTLDVI 89

Immunoglobulin I-set domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1); The members here are composed of the immunoglobulin I-set (IgI) domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1). Human Lingo-1 is a central nervous system-specific transmembrane glycoprotein also known as LERN-1, which functions as a negative regulator of neuronal survival, axonal regeneration, and oligodendrocyte differentiation and myelination. Lingo-1 is a key component of the Nogo receptor signaling complex (RTN4R/NGFR) in RhoA activation responsible for some inhibition of axonal regeneration by myelin-associated factors. The ligand-binding ectodomain of human Lingo-1 contains a bimodular, kinked structure composed of leucine-rich repeat (LRR) and immunoglobulin (Ig)-like modules. Diseases associated with Lingo-1 include mental retardation, autosomal recessive 64 and essential tremor. 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 the Lingo-1 lacks this strand and thus it 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.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 253 KVGEVFTVDLGEAILFDCSADSHPPNTYSWIRR-------TDNTTYIIKHGPRLEVaSEKVAQKTMDYVCCAYNNITGRQ 325
Cdd:cd20969   7 RKAQQVFVDEGHTVQFVCRADGDPPPAILWLSPrkhlvsaKSNGRLTVFPDGTLEV-RYAQVQDNGTYLCIAANAGGNDS 85

                ....*..
gi 86439957 326 DETHFTV 332
Cdd:cd20969  86 MPAHLHV 92

First immunoglobulin variable (IgV) domain of poliovirus receptor (PVR, also known as CD155 and necl-5), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (necl-5)). Poliovirus (PV) binds to its cellular receptor (PVR/CD155) to initiate infection. CD155 is a membrane-anchored, single-span glycoprotein; its extracellular region has three Ig-like domains. There are four different isotypes of CD155 (referred to as alpha, beta, gamma, and delta), that result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted; CD155-alpha and CD155-delta are membrane-bound and function as PV receptors. The virus recognition site is contained in the amino-terminal domain, D1. Having the virus attachment site on the receptor distal from the plasma membrane may be important for successful initiation of infection of cells by the virus. CD155 binds in the poliovirus "canyon" with a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the first Ig-like domain of nectin-1 (also known as poliovirus receptor related protein(PVRL)1; CD111), nectin-3 (also known as PVRL 3), nectin-4 (also known as PVRL4; LNIR receptor)and DNAX accessory molecule 1 (DNAM-1; CD226).

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957  34 VTVPSHtVHGVRGQALYLPVHYGFHTPASDIQIIWLFERPHTM-------PKYllG-SVNKSVVPDLEYQHKFtMMPPNA 105
Cdd:cd05718   3 VQVPTE-VTGFLGGSVTLPCSLTSPGTTKITQVTWMKIGAGSSqnvavfhPQY--GpSVPNPYAERVEFLAAR-LGLRNA 78

                        90       100       110
                ....*....|....*....|....*....|....
gi 86439957 106 SLLINPLQFPDEGNYIVKV------NIQGNGTLS 133
Cdd:cd05718  79 TLRIRNLRVEDEGNYICEFatfpqgNRQGTTWLR 112

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 157 SGAVEYVGNMTLTCHVEGgTRLAYQWLKNGRPVHTSSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRNPVSEMESDiimpi 236
Cdd:cd05740   9 SNPVEDKDAVTLTCEPET-QNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANRSD----- 82

                        90
                ....*....|.
gi 86439957 237 iyygPYGLQVN 247
Cdd:cd05740  83 ----PVTLDVI 89

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957   149 PVVQIHPPSGAVEYVGNMTLTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNN--TLHIAPVTKEDIGNYSCLVRNPVS 226
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDRFKVTYEGGtyTLTISNVQPDDSGKYTCVATNSAG 80

                  ....*.
gi 86439957   227 EMESDI 232
Cdd:pfam07679  81 EAEASA 86

Second immunoglobulin (Ig)-like domain of a Follistatin-related protein 5, and similar domains; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain found in human Follistatin-related protein 5 (FSTL5) and a follistatin-like molecule encoded by the CNS-related Mahya gene. Mahya genes have been retained in certain Bilaterian branches during evolution. They are conserved in Hymenoptera and Deuterostomes, but are absent from other metazoan species such as fruit fly and nematode. Mahya proteins are secretory, with a follistatin-like domain (Kazal-type serine/threonine protease inhibitor domain and EF-hand calcium-binding domain), two Ig-like domains, and a novel C-terminal domain. Mahya may be involved in learning and memory and in processing of sensory information in Hymenoptera and vertebrates. Follistatin is a secreted, multidomain protein that binds activins with high affinity and antagonizes their signaling.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 149 PVVQIHPPSGAVEYVGNMTLTCHVEGGTRLAYQWLKNGRPVHT--SSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRNPVS 226
Cdd:cd05736   1 PVIRVYPEFQAKEPGVEASLRCHAEGIPLPRVQWLKNGMDINPklSKQLTLIANGSELHISNVRYEDTGAYTCIAKNEGG 80

                ....*.
gi 86439957 227 eMESDI 232
Cdd:cd05736  81 -VDEDI 85

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

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 86439957    164 GNMTLTCHVEGGTRLAYQWLKNG-RPVHTSSTYSFSPQNN--TLHIAPVTKEDIGNYSCLVRN 223
Cdd:smart00410  10 ESVTLSCEASGSPPPEVTWYKQGgKLLAESGRFSVSRSGStsTLTISNVTPEDSGTYTCAATN 72

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 86439957 167 TLTCHVEGGTRLAYQWLKNGRPVHT-SSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRNPVSEMESDIIMPI 236
Cdd:cd05730  22 TLACDADGFPEPTMTWTKDGEPIESgEEKYSFNEDGSEMTILDVDKLDEAEYTCIAENKAGEQEAEIHLKV 92

First immunoglobulin (Ig) domain of contactin; member of the I-set of (Ig) superfamily domains; The members here are composed of the first 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. This group belongs to the I-set of IgSF domains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 149 PVVQIHP-----PSGAVEyvGNMTLTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNNTLHIA-PVTKEDIGNYSCLVR 222
Cdd:cd04967   2 PVFEEQPddtifPEDSDE--KKVALNCRARANPVPSYRWLMNGTEIDLESDYRYSLVDGTLVISnPSKAKDAGHYQCLAT 79

                ....*...
gi 86439957 223 NPVSEMES 230
Cdd:cd04967  80 NTVGSVLS 87

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. 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 second Ig-like domain of JAM1 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, the A strand of the I-set is discontinuous but lacks 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.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 149 PVVQIhpPSGAVeyVGN-MTLTCHVEGGTRLA-YQWLKNGRPVHT---------SSTYSFSPQNNTLHIAPVTKEDIGNY 217
Cdd:cd20950   1 PTVNI--PSSAT--IGNrAVLTCSEPDGSPPSeYTWFKDGVVMPTnpkstrafsNSSYSLDPTTGELVFDPLSASDTGEY 76

                ....*.
gi 86439957 218 SCLVRN 223
Cdd:cd20950  77 SCEARN 82

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.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 164 GNMT-LTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNN---TLHIAPVTKEDIGNYSCLVRNPVSEME 229
Cdd:cd05744  15 GRLCrFDCKVSGLPTPDLFWQLNGKPVRPDSAHKMLVRENgrhSLIIEPVTKRDAGIYTCIARNRAGENS 84

First immunoglobulin (Ig) domain of contactin-5; member of the I-set of Ig superfamily domains; The members here are composed of the first immunoglobulin (Ig) domain of the neural cell adhesion molecule contactin-5. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains, anchored to the membrane by glycosylphosphatidylinositol. The different contactins show different expression patterns in the central nervous system. In rats, a lack of contactin-5 (NB-2) results in an impairment of the neuronal activity in the auditory system. Contactin-5 is expressed specifically in the postnatal nervous system, peaking at about 3 weeks postnatal. Contactin-5 is highly expressed in the adult human brain in the occipital lobe and in the amygdala; lower levels of expression have been detected in the corpus callosum, caudate nucleus, and spinal cord. This group belongs to the I-set of IgSF domains.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 86439957 166 MTLTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNNTLHIA-PVTKEDIGNYSCLVRNPVSEMES 230
Cdd:cd05848  22 VILNCEARGNPVPTYRWLRNGTEIDTESDYRYSLIDGNLIISnPSEVKDSGRYQCLATNSIGSILS 87

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.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 86439957 159 AVEYVGNMTLTCHVEGGTRLAYQWLKNGRPV---HTSSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRN 223
Cdd:cd05857  15 AVPAANTVKFRCPAAGNPTPTMRWLKNGKEFkqeHRIGGYKVRNQHWSLIMESVVPSDKGNYTCVVEN 82

Fourth immunoglobulin (Ig)-like domain of peroxidasin; The members here are composed of the fourth 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.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 86439957 168 LTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNnTLHIAPVTKEDIGNYSCLVRNPVSEMESDIIM 234
Cdd:cd05746   3 IPCSAQGDPEPTITWNKDGVQVTESGKFHISPEG-YLAIRDVGVADQGRYECVARNTIGYASVSMVL 68

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
                ....*....|....*....|....*....|....*....|....*....
gi 86439957 182 WLKNGRPVHTSSTYSFSPQNNTLHIAPVTKEDIGNYSCLVRNPVSEMES 230
Cdd:cd05724  32 WRKDGQPLNLDNERVRIVDDGNLLIAEARKSDEGTYKCVATNMVGERES 80

Immunoglobulin Constant-1 (C1)-set domain; The members here are composed of C1-set domains, classical Ig-like domains resembling the antibody constant domain. Members of the IgC1 family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, while the IgC domain is involved in oligomerization and molecular interactions. 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 strands by G, F, C, and C'.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 86439957 151 VQIHPPSGAVEYVGNMTLTCHVEGGTR--LAYQWLKNGRPVHTSSTYSFSPQNN--------TLHIAPVTKEDIGNYSCL 220
Cdd:cd00098   2 VTLLPPSPEEKGGGKVTLVCLVSGFYPkdITVTWLKNGVPLTSGVSTSSPVEPNdgtysvtsSLTVPPSDWDEGATYTCV 81

                ....
gi 86439957 221 VRNP 224
Cdd:cd00098  82 VTHE 85

Fourth Ig domain of the neural cell adhesion molecule contactin-2, and similar domains; The members here are composed of the fourth Ig domain of the neural cell adhesion molecule contactin-2. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-2 (also called TAG-1, axonin-1) facilitates cell adhesion by homophilic binding between molecules in apposed membranes. The first four Ig domains form the intermolecular binding fragment which arranges as a compact U-shaped module by contacts between Ig domains 1 and 4, and domains 2 and 3. It has been proposed that a linear zipper-like array forms, from contactin-2 molecules alternatively provided by the two apposed membranes.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|....
gi 86439957 170 CHVEGGTRLAYQWLKNGRPVHTSSTYSFSpqNNTLHIAPVTKEDIGNYSCLVRN 223
Cdd:cd05728  21 CKASGNPRPAYRWLKNGQPLASENRIEVE--AGDLRITKLSLSDSGMYQCVAEN 72

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
                ....*....|....*....|....*....|....*....|....*....|....*...
gi 86439957 180 YQWLKNGRPVHTSSTYSfspQNNTLHIAPVTKEDIGNYSCLVRNPVSEMESDIIMPII 237
Cdd:cd04976  35 VVWYKDGLPLTEKARYL---TRHSLIIKEVTEEDTGNYTILLSNKQSNVFKNLTATLV 89

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.

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gi 86439957 256 EVFTVDLGEAILFDCSADSHPPNTYSWIRR----TDNTTYIIKHGPRLEVASEKVAQKTMdYVCCAYNNITGRQ 325
Cdd:cd20957   9 PVQTVDFGRTAVFNCSVTGNPIHTVLWMKDgkplGHSSRVQILSEDVLVIPSVKREDKGM-YQCFVRNDGDSAQ 81

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.

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gi 86439957 168 LTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNNTLH---IAPVTKEDIGNYSCLVRN 223
Cdd:cd20990  20 MDCKVSGLPTPDLSWQLDGKPIRPDSAHKMLVRENGVHsliIEPVTSRDAGIYTCIATN 78

Sixth 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 sixth 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.

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gi 86439957 157 SGAVEYVGNMTLTCHVEGG-TRLAYQWLKNGRPVHTSSTYSFS---PQNNTLHIAPVTKEDIGNYSCLVRNPVSEME 229
Cdd:cd20959  11 EGAAQVGMRAQLHCGVPGGdLPLNIRWTLDGQPISDDLGITVSrlgRRSSILSIDSLEASHAGNYTCHARNSAGSAS 87

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM. Human HLA-DM plays a critical role in antigen presentation to CD4 T cells by catalyzing the exchange of peptides bound to MHC class II molecules. Type 1 diabetes is correlated with DM activation and it is also implicated in viral infections such as herpes simplex virus, celiac disease, multiple sclerosis, other autoimmune diseases, and leukemia. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

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gi 86439957 147 TKPVVQIHP--PSGAVEYVgnMtLTCHVEG--GTRLAYQWLKNGRPVHTSSTYSFSPQNN------TLHIAPVTKEDIGN 216
Cdd:cd21002   2 RPPSVRVAPttPFNTREPV--M-LACHVWGfyPADVTITWLKNGDPVAPHSSAPKTAQPNgdwtyqTQVTLAVTPSPGDT 78

                ....*
gi 86439957 217 YSCLV 221
Cdd:cd21002  79 YTCSV 83

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. 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, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), 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 Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 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.

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gi 86439957 153 IHPPSGAVEYVGN-MTLTCHVEGGTRLAYQWLKNGRPVHTSSTYSFS-----PQNNTLHIAPV----TKEDIGNYSCLVR 222
Cdd:cd07693   4 VEHPSDLIVSKGDpATLNCKAEGRPTPTIQWLKNGQPLETDKDDPRShrivlPSGSLFFLRVVhgrkGRSDEGVYVCVAH 83

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gi 86439957 223 NPVSEMES 230
Cdd:cd07693  84 NSLGEAVS 91

C-terminal immunoglobulin (Ig)-like domain of myomesin and M-protein; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of myomesin and M-protein (also known as myomesin-2). Myomesin and M-protein are both structural proteins localized to the M-band, a transverse structure in the center of the sarcomere, and are candidates for M-band bridges. Both proteins are modular, consisting mainly of repetitive Ig-like and fibronectin type III (FnIII) domains. Myomesin is expressed in all types of vertebrate striated muscle; M-protein has a muscle-type specific expression pattern. Myomesin is present in both slow and fast fibers; M-protein is present only in fast fibers. It has been suggested that myomesin acts as a molecular spring with alternative splicing as a means of modifying its elasticity.

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gi 86439957 166 MTLTCHVEGGTRLAYQWLKNGRPVHTSSTYSFSPQNN---TLHIAPVTKEDIGNYSCLVRNPVSEMESDIIMPI 236
Cdd:cd05737  19 LNLTCNVWGDPPPEVSWLKNDQALAFLDHCNLKVEAGrtvYFTINGVSSEDSGKYGLVVKNKYGSETSDVTVSV 92

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM), and similar domains; The members here are composed of the third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, and spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM and human neurofascin.

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gi 86439957 164 GNMTLTCHVEGGTRLAYQWLK-NGR-PVHTSSTYSFspqNNTLHIAPVTKEDIGNYSCLVRNPV 225
Cdd:cd05731  11 GVLLLECIAEGLPTPDIRWIKlGGElPKGRTKFENF---NKTLKIENVSEADSGEYQCTASNTM 71

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 86439957 179 AYQWLKNGRPVHTSSTYSfspQNNTLHIAPVTKEDIGNYSCLVRNPVSEME 229
Cdd:cd05864  33 EIKWYKNGIPIESNHTIK---AGHVLTIMEVTEKDAGNYTVVLTNPISKEK 80