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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D        7 VEQTPTTTTKEAGESLTINCVLRDSpCSLDSTFWYFTKKG---------ATKKENLSNG--GRYAETVNKaSKSFSLQIS 75
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVSSS-FSSTYIYWYRQKPGqgpefliylSSSKGKTKGGvpGRFSGSRDG-TSSFSLTIS 78

                        90       100       110
                ....*....|....*....|....*....|....*....
7FBK_D       76 DLRVEDSGTYHCrAYSTTGDERDcrwqgYIEGYGTIVTV 114
Cdd:cd00099  79 NLQPEDSGTYYC-AVSESGGTDK-----LTFGSGTRLTV 111

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D        7 VEQTPTTTTKEAGESLTINCVLRDSpCSLDSTFWYFTKKG---------ATKKENLSNG--GRYAETVNKaSKSFSLQIS 75
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVSSS-FSSTYIYWYRQKPGqgpefliylSSSKGKTKGGvpGRFSGSRDG-TSSFSLTIS 78

                        90       100       110
                ....*....|....*....|....*....|....*....
7FBK_D       76 DLRVEDSGTYHCrAYSTTGDERDcrwqgYIEGYGTIVTV 114
Cdd:cd00099  79 NLQPEDSGTYYC-AVSESGGTDK-----LTFGSGTRLTV 111

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D          11 PTTTTKEAGESLTINCVLRDSPcsLDSTFWYFTKKgatkkENLSNGGRYaeTVNKASKSFSLQISDLRVEDSGTYHCRAY 90
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSP--PPEVTWYKQGG-----KLLAESGRF--SVSRSGSTSTLTISNVTPEDSGTYTCAAT 71

                   ....*.
7FBK_D          91 STTGDE 96
Cdd:smart00410  72 NSSGSA 77

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D        7 VEQTPTTTTKEAGESLTINCVLRDSpCSLDSTFWYFTKKG---------ATKKENLSNG--GRYAETVNKaSKSFSLQIS 75
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVSSS-FSSTYIYWYRQKPGqgpefliylSSSKGKTKGGvpGRFSGSRDG-TSSFSLTIS 78

                        90       100       110
                ....*....|....*....|....*....|....*....
7FBK_D       76 DLRVEDSGTYHCrAYSTTGDERDcrwqgYIEGYGTIVTV 114
Cdd:cd00099  79 NLQPEDSGTYYC-AVSESGGTDK-----LTFGSGTRLTV 111

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D          9 QTPTTTTKEAGESLTINCVLRDSPCS-LDSTFWYFTKKGA----------TKKENLSNGGRYAETVNKASKSFSLQISDL 77
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSSMSEaSTSVYWYRQPPGKgptfliayysNGSEEGVKKGRFSGRGDPSNGDGSLTIQNL 80

                          90       100       110
                  ....*....|....*....|....*....|....*..
7FBK_D         78 RVEDSGTYHCRAYSTTGDerdcrwqgyIEGYGTIVTV 114
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEG---------VFGKGTRLTV 108

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) delta chain; The members here are composed of the immunoglobulin (Ig) variable (V) domain of the delta 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 antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma/delta TCRs recognize intact protein antigens; they recognize protein antigens directly and without antigen processing, and 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 standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D        6 RVEQTPTTTTKEAGESLTINCVLRDSPCSLDsTFWY---------FTKKGATKKENLSNGgRYAETVNKASKSFSLQISD 76
Cdd:cd07706   1 KVTQAQPDVSVQVGEEVTLNCRYETSWTNYY-LFWYkqlpsgemtFLIRQDSSEQNAKSG-RYSVNFQKAQKSISLTISA 78

                        90       100       110
                ....*....|....*....|....*....|....*...
7FBK_D       77 LRVEDSGTYHCrAYSTTGDErdcrwQGYIEGYGTIVTV 114
Cdd:cd07706  79 LQLEDSAKYFC-ALSLPYDT-----DKLIFGKGTRLTV 110

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D        7 VEQTPTTTTKEAGESLTINCVLRDSPCSLDSTFWYFTKKG-------------ATKKENLSNGGRYAETVNKASKSFSLQ 73
Cdd:cd04982   1 LEQPQLSITREESKSVTISCKVSGIDFSTTYIHWYRQKPGqalerllyvsstsAVRKDSGKTKNKFEARKDVGKSTSTLT 80

                        90       100       110       120
                ....*....|....*....|....*....|....*....|....
7FBK_D       74 ISDLRVEDSGTYHCRAYsttgderDCRWQGYIE--GYGT--IVT 113
Cdd:cd04982  81 ITNLEKEDSATYYCAYW-------ESGSGYYIKvfGSGTklIVT 117

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
7FBK_D          21 SLTINCVLRDSPCSLDSTFWYFTKKG------------ATKKENLSNGGRYAETVNKASKSFSLQISDLRVEDSGTYHC 87
Cdd:smart00406   1 SVTLSCKFSGSTFSSYYVSWVRQPPGkglewlgyigsnGSSYYQESYKGRFTISKDTSKNDVSLTISNLRVEDTGTYYC 79

N-terminal immunoglobulin (Ig)-like domain of the signaling lymphocyte activation molecule (SLAM) family; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the signaling lymphocyte activation molecule (SLAM) family and similar proteins. The SLAM family is a group of immune-cell specific receptors that can regulate both adaptive and innate immune responses. Members of this group include proteins such as CD84, SLAM (CD150), Ly-9 (CD229), NTB-A (ly-108, SLAM6), 19A (CRACC), and SLAMF9. The genes coding for the SLAM family are nested on chromosome 1, in humans at 1q23, and in mice at 1H2. The SLAM family is a subset of the CD2 family, which also includes CD2 and CD58 located on chromosome 1 at 1p13 in humans. In mice, CD2 is located on chromosome 3, and there is no CD58 homolog. The SLAM family proteins are organized as an extracellular domain with either two or four Ig-like domains, a single transmembrane segment, and a cytoplasmic region having Tyr-based motifs. The extracellular domain is organized as a membrane-distal Ig variable (IgV) domain that is responsible for ligand recognition and a membrane-proximal truncated Ig constant-2 (IgC2) domain.

                        10        20        30
                ....*....|....*....|....*....|....*.
7FBK_D       58 RYAETVNKASKSFSLQISDLRVEDSGTYhcRAYSTT 93
Cdd:cd16842  53 SYKERLNISQNDYSLQISNLTMEDAGSY--RARINT 86

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
                ....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D       57 GRYAETVNKASKSFSLQISDLRVEDSGTYHCrAYSTTGDerdcrWQGYIE--GYGTIVTV 114
Cdd:cd04981  64 GRFTITRDTSKSTAYLQLNSLTSEDTAVYYC-ARGLGGY-----GYSYFDywGQGTTVTV 117

T-cell receptor Mu, Heavy chain, variable (V) domain; The members here are composed of the immunoglobulin (Ig) heavy chain (H), variable (V) domain of the T-cell receptor Mu. 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. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|....*....
7FBK_D       56 GGRYAETVNKASKSFSLQISDLRVEDSGTYHCRAYSTTGDERDcrwqGYIEGYGTIVTV 114
Cdd:cd16095  60 EDRITSSREDTNSQIFLQIKGLGLRDSGQYHCARRVGYGDDTD----KLIFGPGTDVIV 114

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*...
7FBK_D       22 LTINCVLRDSPcsLDSTFWYftkKGATKKENLSNGGRYAETVNkasksFSLQISDLRVEDSGTYHCRA 89
Cdd:cd00096   1 VTLTCSASGNP--PPTITWY---KNGKPLPPSSRDSRRSELGN-----GTLTISNVTLEDSGTYTCVA 58

N-terminal immunoglobulin (Ig)-like domain of T-cell surface antigen CD2, and similar domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain (or domain 1) of T-cell surface antigen Clusters of Differentiation (CD) 2 and similar proteins. CD2 is a T-cell specific surface glycoprotein and is critically important for mediating adhesion between T cells and antigen-presenting cells or between cytolytic T cells and target cells. CD2 is located on chromosome 1 at 1p13 in humans and on chromosome 3 in mice. CD2 contains an extracellular domain with two or Ig-like domains, a single transmembrane segment, and a cytoplasmic region rich in proline and basic residues.

                        10        20        30
                ....*....|....*....|....*....|....*...
7FBK_D       68 KSFSLQISDLRVEDSGTYHCRAYSTTGDERDCRWQGYI 105
Cdd:cd05775  60 ESGSLTIKNLTKEDSGTYELEITSTNGKVLSSKFTLEV 97

Immunoglobulin (Ig)-like domain of vascular endothelial growth factor (VEGF) receptor (R) and similar proteins; member of the I-set of IgSF domains; The members here are composed of the immunoglobulin (Ig)-like domain of vascular endothelial growth factor (VEGF) receptor (R) and related proteins. 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). VEGF-A interacts with both VEGFR-1 and VEGFR-2. VEGFR-1 binds strongest to VEGF; VEGF-2 binds more weakly. VEGFR-3 appears not to bind VEGF, but binds other members of the VEGF family (VEGF-C and -D). VEGFRs bind VEGFs with high affinity with 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 also contains alpha-type platelet-derived growth factor receptor precursor (PDGFR)-alpha (CD140a), and PDGFR-beta (CD140b). PDGFRs alpha and beta have an extracellular component with five Ig-like domains, a transmembrane segment, and a cytoplasmic portion that has protein tyrosine kinase activity.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
7FBK_D       14 TTKEAGESLTINCVLRdSPCSLDSTF-WYFTKKgatKKENLSNGGRYAETVNKASKSFS--LQISDLRVEDSGTYHCRAY 90
Cdd:cd05742  12 TVLPQGETLVLNCTAN-VNLNEVVDFqWTYPSE---KEGKLALLKPDIKVDWSEPGEFVstLTIPEATLKDSGTYTCAAR 87

                ...
7FBK_D       91 STT 93
Cdd:cd05742  88 SGV 90

Immunoglobulin (Ig)-like domain of human cartilage link protein (LP), and similar domains; The members here are composed of the immunoglobulin (Ig)-like domain similar to that found in human cartilage link protein (LP; also called hyaluronan and proteoglycan link protein). In cartilage, chondroitin-keratan sulfate proteoglycan (CSPG), aggrecan, forms cartilage link protein stabilized aggregates with hyaluronan (HA). These aggregates contribute to the tissue's load bearing properties. Aggregates having other CSPGs substituting for aggrecan may contribute to the structural integrity of many different tissues. Members of the vertebrate HPLN (hyaluronan/HA and proteoglycan binding link) protein family are physically linked adjacent to CSPG genes.

                        10
                ....*....|....*..
7FBK_D       71 SLQISDLRVEDSGTYHC 87
Cdd:cd05877  79 SLVITDLRLEDYGRYRC 95

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
                ....*....|....*....|....*....|..
7FBK_D       57 GRYAETVNKASKSFSLQISDLRVEDSGTYHCR 88
Cdd:cd20960  68 GRVAFTSNDLSGDASLNISNLKLSDTGTYQCK 99