Immunoglobulin (Ig) heavy chain (H), variable (V) domain; The members here are composed of the immunoglobulin (Ig) heavy chain (H), variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. 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. There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which can associate with any of the heavy chains. This family includes alpha, gamma, delta, epsilon, and mu heavy chains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617   3 QLVQSGPELKKPGETVKISCKASGYTFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYADDFKGRFAFSLETSASTAYLQ 82
Cdd:cd04981     1 QLQESGPGLVKPGQSLKLSCKASGFTFTSYGMGWVRQAPGKGLEWIGLIYPGGGDTYYADSFKGRFTITRDTSKSTAYLQ 80

                          90       100       110
                  ....*....|....*....|....*....|....*...
gi 2211113617  83 INNLKNEDTATYFCAR-------WDGAYWGQGTLVTVS 113
Cdd:cd04981    81 LNSLTSEDTAVYYCARglggygySYFDYWGQGTTVTVS 118

Immunoglobulin (Ig) heavy chain (H), variable (V) domain; The members here are composed of the immunoglobulin (Ig) heavy chain (H), variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. 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. There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which can associate with any of the heavy chains. This family includes alpha, gamma, delta, epsilon, and mu heavy chains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617   3 QLVQSGPELKKPGETVKISCKASGYTFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYADDFKGRFAFSLETSASTAYLQ 82
Cdd:cd04981     1 QLQESGPGLVKPGQSLKLSCKASGFTFTSYGMGWVRQAPGKGLEWIGLIYPGGGDTYYADSFKGRFTITRDTSKSTAYLQ 80

                          90       100       110
                  ....*....|....*....|....*....|....*...
gi 2211113617  83 INNLKNEDTATYFCAR-------WDGAYWGQGTLVTVS 113
Cdd:cd04981    81 LNSLTSEDTAVYYCARglggygySYFDYWGQGTTVTVS 118

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 2211113617  15 GETVKISCKASGY-TFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYaddFKGRFAFSLETSASTAYLQINNLKNEDTAT 93
Cdd:pfam07686  11 GGSVTLPCTYSSSmSEASTSVYWYRQPPGKGPTFLIAYYSNGSEEGV---KKGRFSGRGDPSNGDGSLTIQNLTLSDSGT 87

                          90       100
                  ....*....|....*....|.
gi 2211113617  94 YFCARW--DGAYWGQGTLVTV 112
Cdd:pfam07686  88 YTCAVIpsGEGVFGKGTRLTV 108

Immunoglobulin (Ig) heavy chain (H), variable (V) domain; The members here are composed of the immunoglobulin (Ig) heavy chain (H), variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. 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. There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which can associate with any of the heavy chains. This family includes alpha, gamma, delta, epsilon, and mu heavy chains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617   3 QLVQSGPELKKPGETVKISCKASGYTFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYADDFKGRFAFSLETSASTAYLQ 82
Cdd:cd04981     1 QLQESGPGLVKPGQSLKLSCKASGFTFTSYGMGWVRQAPGKGLEWIGLIYPGGGDTYYADSFKGRFTITRDTSKSTAYLQ 80

                          90       100       110
                  ....*....|....*....|....*....|....*...
gi 2211113617  83 INNLKNEDTATYFCAR-------WDGAYWGQGTLVTVS 113
Cdd:cd04981    81 LNSLTSEDTAVYYCARglggygySYFDYWGQGTTVTVS 118

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 2211113617   4 LVQSGPEL-KKPGETVKISCKASGyTFTTYGMSWVKQAPGKGLKWMgwINTYSGVPTYADDFKGRFAFSLEtSASTAYLQ 82
Cdd:cd00099     1 VTQSPRSLsVQEGESVTLSCEVSS-SFSSTYIYWYRQKPGQGPEFL--IYLSSSKGKTKGGVPGRFSGSRD-GTSSFSLT 76

                          90       100       110
                  ....*....|....*....|....*....|....*
gi 2211113617  83 INNLKNEDTATYFCARWDG-----AYWGQGTLVTV 112
Cdd:cd00099    77 ISNLQPEDSGTYYCAVSESggtdkLTFGSGTRLTV 111

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) gamma chain; The members here are composed of the immunoglobulin (Ig) variable (V) domain of the gamma chain of gamma/delta T-cell receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are heterodimers consisting of alpha and beta chains or gamma and delta chains. Each chain contains a variable (V) and a constant (C) region. The majority of T cells contain alpha/beta TCRs, but a small subset contain gamma/delta TCRs. Alpha/beta TCRs recognize antigens as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Gamma/delta T cells can also be stimulated by non-peptide antigens such as small phosphate- or amine-containing compounds. The variable domain of gamma/delta TCRs is responsible for antigen recognition and is located at the N-terminus of the receptor. Members of this group contain the standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617  12 KKPGETVKISCKASGYTFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYADDFKGRFAFSLETSASTAYLQINNLKNEDT 91
Cdd:cd04982    10 REESKSVTISCKVSGIDFSTTYIHWYRQKPGQALERLLYVSSTSAVRKDSGKTKNKFEARKDVGKSTSTLTITNLEKEDS 89

                          90       100
                  ....*....|....*....|....*...
gi 2211113617  92 ATYFCARWDGA--YW----GQGTLVTVS 113
Cdd:cd04982    90 ATYYCAYWESGsgYYikvfGSGTKLIVT 117

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617    7 SGPELKKPGETVKISCKASGytFTTYGMSWVKQapgkGLKWMGwintysgvptyaddFKGRFafSLETSASTAYLQINNL 86
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASG--SPPPEVTWYKQ----GGKLLA--------------ESGRF--SVSRSGSTSTLTISNV 58

                           90       100
                   ....*....|....*....|....*..
gi 2211113617   87 KNEDTATYFCARWDGAYWGQG-TLVTV 112
Cdd:smart00410  59 TPEDSGTYTCAATNSSGSASSgTTLTV 85

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) alpha chain and similar proteins; The members here are composed of the immunoglobulin (Ig) variable domain of the alpha chain of alpha/beta T-cell antigen receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are composed of alpha and beta, or gamma and delta polypeptide chains with variable (V) and constant (C) regions. This group represents the variable domain of the alpha chain of TCRs and also includes the variable domain of delta chains of TCRs. Alpha/beta TCRs recognize antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. The variable domain of TCRs is responsible for antigen recognition, and is located at the N-terminus of the receptor. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617   1 QIQLVQSGPElkkpGETVKISCKASgyTFTTYGMSWVKQAPGKGLKWMgwINTYSGVPTYAddfKGRFAFSLETSASTAY 80
Cdd:cd04983     3 QSPQSLSVQE----GENVTLNCNYS--TSTFYYLFWYRQYPGQGPQFL--IYISSDSGNKK---KGRFSATLDKSRKSSS 71

                          90       100       110
                  ....*....|....*....|....*....|....*..
gi 2211113617  81 LQINNLKNEDTATYFCA--RWDGAY---WGQGTLVTV 112
Cdd:cd04983    72 LHISAAQLSDSAVYFCAlsESGGTGkltFGKGTRLTV 108

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 2211113617  15 GETVKISCKASGY-TFTTYGMSWVKQAPGKGLKWMGWINTYSGVPTYaddFKGRFAFSLETSASTAYLQINNLKNEDTAT 93
Cdd:pfam07686  11 GGSVTLPCTYSSSmSEASTSVYWYRQPPGKGPTFLIAYYSNGSEEGV---KKGRFSGRGDPSNGDGSLTIQNLTLSDSGT 87

                          90       100
                  ....*....|....*....|.
gi 2211113617  94 YFCARW--DGAYWGQGTLVTV 112
Cdd:pfam07686  88 YTCAVIpsGEGVFGKGTRLTV 108

Immunoglobulin (Ig) variable (V) domain of Cluster of Differentiation (CD) 8 beta chain; The members here are composed of the immunoglobulin (Ig)-like domain in Cluster of Differentiation (CD) 8 beta. The CD8 glycoprotein plays an essential role in the control of T-cell selection, maturation, and the T-cell receptor (TCR)-mediated response to peptide antigen. CD8 is comprised of alpha and beta subunits and is expressed as either an alpha/alpha or alpha/beta dimer. Both dimeric isoforms can serve as a coreceptor for T cell activation and differentiation, however they have distinct physiological roles, different cellular distributions, unique binding partners, etc. Each CD8 subunit is comprised of an extracellular domain containing a V-type Ig-like domain, a single pass transmembrane portion, and a short intracellular domain. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617  17 TVKISCKASGYTFTTyGMSWVK--QAPGKG------LKWmgwinTYSGVPTYADDFKG-RFAFSLETSASTAYLQINNLK 87
Cdd:cd07700    15 TVKMSCEAKTSPKNT-RIYWLRqrQAPSKDshfeflASW-----DPSKGIVYGEGVDQeKLIILSDSDSSRYILSLMSVK 88

                          90
                  ....*....|
gi 2211113617  88 NEDTATYFCA 97
Cdd:cd07700    89 PEDSGTYFCM 98

Immunoglobulin Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins; The members here are composed of the Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins. CAR, which is encoded by human CXADR gene, is a cell adhesion molecule of the Immunoglobulin (Ig) superfamily. The CAR acts as a type I membrane receptor for group B1-B6 coxsackie viruses and subgroup C adenoviruses. For instance, adenovirus interacts with the coxsackievirus and adenovirus receptor to enter epithelial airway cells. The CAR is also shown to be involved in physiological processes such as neuronal and heart development, epithelial tight junction integrity, and tumor suppression. The CAR is a component of the epithelial apical junction complex that may function as a homophilic cell adhesion molecule and is essential for tight junction integrity. The CAR is also involved in transepithelial migration of leukocytes through adhesive interactions with JAML a transmembrane protein of the plasma membrane of leukocytes. The interaction between both receptors also mediates the activation of gamma-delta T-cells, a subpopulation of T-cells residing in epithelia and involved in tissue homeostasis and repair. The CAR is composed of one V-set and one C2-set Ig module, a single transmembrane helix, and an intracellular domain. This group belongs to the V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2211113617  10 ELKK-PGETVKISCKasgYTFT-----TYGMSWVKQAPGKGLKWmgwINTYSG---VPTYADDFKGRFAFSLETSASTAY 80
Cdd:cd20960     9 EIKKvAGENVTLPCH---HQLGledqgTLDIEWLLLPSDKVEKV---VITYSGdrvYNHYYPALKGRVAFTSNDLSGDAS 82

                          90
                  ....*....|....*.
gi 2211113617  81 LQINNLKNEDTATYFC 96
Cdd:cd20960    83 LNISNLKLSDTGTYQC 98

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
                  ....*....|....*....|....*....|....*....|....*....
gi 2211113617  65 KGRFAFSLETSASTAYLQINNLKNEDTATYFCARWDGAYWGQGTLVTVS 113
Cdd:cd05716    52 GGRISLTDDPDNGVFTVTLNQLRKEDAGWYWCGVGDDGDRGLTVQVKLV 100