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 530414082 140 IVSEPGKNVTLTCQPQMTWPVQAVRWEKIQPrqidllTYCN-LVHGRNFTSKFPRQIVSNCSHGRWSViVIPDVTVSDSG 218
Cdd:cd05716    7 VTGVEGGSVTIQCPYPPKYASSRKYWCKWGS------EGCQtLVSSEGVVPGGRISLTDDPDNGVFTV-TLNQLRKEDAG 79

                 ....
gi 530414082 219 LYRC 222
Cdd:cd05716   80 WYWC 83

Immunoglobulin (Ig)-like domain in the polymeric Ig receptor (pIgR) and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain in the polymeric Ig receptor (pIgR) and similar proteins. pIgR delivers dimeric IgA and pentameric IgM to mucosal secretions. Polymeric immunoglobulin (pIgs) are the first defense against pathogens and toxins. IgA and IgM can form polymers via an 18-residue extension at their C-termini referred to as the tailpiece. pIgR transports pIgs across mucosal epithelia into mucosal secretions. Human pIgR is a glycosylated type I transmembrane protein, comprised of a 620-residue extracellular region, a 23-residue transmembrane region, and a 103-residue cytoplasmic tail. The extracellular region contains five domains that share sequence similarity with Ig variable (v) regions. This group also contains the Ig-like extracellular domains of other receptors such as NK cell receptor Nkp44 and myeloid receptors, among others.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082 140 IVSEPGKNVTLTCQPQMTWPVQAVRWEKIQPrqidllTYCN-LVHGRNFTSKFPRQIVSNCSHGRWSViVIPDVTVSDSG 218
Cdd:cd05716    7 VTGVEGGSVTIQCPYPPKYASSRKYWCKWGS------EGCQtLVSSEGVVPGGRISLTDDPDNGVFTV-TLNQLRKEDAG 79

                 ....
gi 530414082 219 LYRC 222
Cdd:cd05716   80 WYWC 83

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082  145 GKNVTLTCQ--PQMTWPVQAVRWEKiQPRQIDLLTYCNLVHGRNFTSKFPRQIVSNCSHGRWSV-IVIPDVTVSDSGLYR 221
Cdd:pfam07686  11 GGSVTLPCTysSSMSEASTSVYWYR-QPPGKGPTFLIAYYSNGSEEGVKKGRFSGRGDPSNGDGsLTIQNLTLSDSGTYT 89

                          90
                  ....*....|....*....
gi 530414082  222 CYLQASAGENETFVMRLTV 240
Cdd:pfam07686  90 CAVIPSGEGVFGKGTRLTV 108

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 530414082  19 EEVLWHTSVPF--AENMSLECVYPSMG--ILTQVEWFKIGT-QQDSIAIFSPTHGMVIRKPYAERVYFLNSTMASNNMTL 93
Cdd:cd05718    1 QRVQVPTEVTGflGGSVTLPCSLTSPGttKITQVTWMKIGAgSSQNVAVFHPQYGPSVPNPYAERVEFLAARLGLRNATL 80

                         90       100       110
                 ....*....|....*....|....*....|...
gi 530414082  94 FFRNASEDDVGYYSCSLYTYPQGTWQKVIQVVQ 126
Cdd:cd05718   81 RIRNLRVEDEGNYICEFATFPQGNRQGTTWLRV 113

First immunoglobulin variable (IgV) domain of nectin-3 (also known as poliovirus receptor related protein 3), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3 (PVRL3) or cluster of differentiation (CD) 113). Nectin-3 belongs to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which participate in adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. For example, during spermatid development, the nectin-3,-2 trans-interaction is required for the formation of Sertoli cell-spermatid junctions in testis, and during morphogenesis of the ciliary body, the nectin-3,-1 trans-interaction is important for apex-apex adhesion between the pigment and non-pigment layers of the ciliary epithelia. Nectins also heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls); nectin-3 for example, trans-interacts with Necl-5, regulating cell movement and proliferation. Other proteins with which nectin-3 interacts include the actin filament-binding protein, afadin, integrin alpha-beta3, Par-3, and PDGF receptor; its interaction with PDGF receptor regulates the latter's signaling for anti-apoptosis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082  24 HTSVPFAENMSLECVYPSMGILTQVEWFKI-GTQQDSIAIFSPTHGMVIRKPYAERVYFLNSTMasNNMTLFFRNASEDD 102
Cdd:cd05887    8 HVTAVWGKNVSLKCLIEVNETITQISWEKIhGKSSQTVAVHHPQYGISIQGEYQGRVSFKNYSL--NDATITLHNVGFSD 85

                         90       100
                 ....*....|....*....|..
gi 530414082 103 VGYYSCSLYTYPQGTWQKVIQV 124
Cdd:cd05887   86 SGKYICKAVTFPLGNAQSSTTV 107

First immunoglobulin variable (IgV) domain of nectin-1, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-1 (also known as poliovirus receptor related protein 1 (PVRL1) or cluster of differentiation (CD) 111). Nectin-1 belongs to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which facilitate adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. In addition nectins heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls), nectin-1 for example, has been shown to trans-interact with Necl-1. Nectins also interact with various other proteins, including the actin filament (F-actin)-binding protein, afadin. Mutation in the human nectin-1 gene is associated with cleft lip/palate ectodermal dysplasia syndrome (CLPED1). Nectin-1 is a major receptor for herpes simplex virus through interaction with the viral envelope glycoprotein D.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 530414082  40 PSMGIlTQVEWFKI--GTQQDsIAIFSPTHGMVIRKPYAERVYFLNSTMasNNMTLFFRNASEDDVGYYSCSLYTYPQG 116
Cdd:cd05886   28 PSVKI-TQVTWQKStnGSKQN-VAIYNPSMGVSVLPPYRERVTFLNPSF--TDGTIRLSRLELEDEGVYICEFATFPTG 102

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 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" strands in the other.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082 136 SNSHIVSEPGKNVTLTCQPQMTWPVQAVRWEKIQPRQ-IDLLTYCNLVHGrNFTSKFPRQIVSNCSHGRWSVIVIPDVTV 214
Cdd:cd00099    4 SPRSLSVQEGESVTLSCEVSSSFSSTYIYWYRQKPGQgPEFLIYLSSSKG-KTKGGVPGRFSGSRDGTSSFSLTISNLQP 82

                         90       100
                 ....*....|....*....|....*....
gi 530414082 215 SDSGLYRCYLQASAGENE-TF--VMRLTV 240
Cdd:cd00099   83 EDSGTYYCAVSESGGTDKlTFgsGTRLTV 111

First immunoglobulin variable (IgV) domain of nectin-3 (also known as poliovirus receptor related protein 3), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3 (PVRL3) or cluster of differentiation (CD) 113). Nectin-3 belongs to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which participate in adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. For example, during spermatid development, the nectin-3,-2 trans-interaction is required for the formation of Sertoli cell-spermatid junctions in testis, and during morphogenesis of the ciliary body, the nectin-3,-1 trans-interaction is important for apex-apex adhesion between the pigment and non-pigment layers of the ciliary epithelia. Nectins also heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls); nectin-3 for example, trans-interacts with Necl-5, regulating cell movement and proliferation. Other proteins with which nectin-3 interacts include the actin filament-binding protein, afadin, integrin alpha-beta3, Par-3, and PDGF receptor; its interaction with PDGF receptor regulates the latter's signaling for anti-apoptosis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082 139 HIVSEPGKNVTLTCQPQMTWPVQAVRWEKIQPRQIDLLTYCNLVHGRNFTSKFPRQIVSNCSHGRWSVIVIPDVTVSDSG 218
Cdd:cd05887    8 HVTAVWGKNVSLKCLIEVNETITQISWEKIHGKSSQTVAVHHPQYGISIQGEYQGRVSFKNYSLNDATITLHNVGFSDSG 87

                 ....
gi 530414082 219 LYRC 222
Cdd:cd05887   88 KYIC 91

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082  134 VPSNSHIVSEpGKNVTLTCQPQMTwPVQAVRWEKIQPRQIDLLTYCNLVHGRNftskfprqivsncshgrwSVIVIPDVT 213
Cdd:pfam13927   6 VSPSSVTVRE-GETVTLTCEATGS-PPPTITWYKNGEPISSGSTRSRSLSGSN------------------STLTISNVT 65

                  ....*....
gi 530414082  214 VSDSGLYRC 222
Cdd:pfam13927  66 RSDAGTYTC 74

Immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG); The members here are composed of the immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG). MOG, a minor component of the myelin sheath, is an important CNS-specific autoantigen, linked to the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). It is a transmembrane protein having an extracellular Ig domain. MOG is expressed in the CNS on the outermost lamellae of the myelin sheath, and on the surface of oligodendrocytes, and may participate in the completion, compaction, and/or maintenance of myelin. This group also includes butyrophilin (BTN). BTN is the most abundant protein in bovine milk-fat globule membrane (MFGM).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 530414082 139 HIVSEPGKNVTLTCQ--PQMTWPVQAVRWEKIQPRQIdlltycnlVH-GRNFTSKFPRQIVS----------NCSHGRWS 205
Cdd:cd05713    9 PILALVGEDAELPCHlsPKMSAEHMEVRWFRSQFSPV--------VHlYRDGQDQEEEQMPEyrgrtellkdAIAEGSVA 80

                         90       100       110
                 ....*....|....*....|....*....|....*.
gi 530414082 206 VIvIPDVTVSDSGLYRCYLQASAGENETfVMRLTVA 241
Cdd:cd05713   81 LR-IHNVRPSDEGQYTCFFRSGSFYEEA-TLELKVA 114