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 3355814   22 IVLTQSIPSLTVSAGERVTISCKSNQNLlwsgnQRYCLVWHQWKPGQTPTPLITWTSDRYSGVPDRFIGSGSVTDFTLTI 101
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSI-----SSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTI 75

                        90       100
                ....*....|....*....|
gi 3355814  102 SSVQAEDVAVYFCQQHLHIP 121
Cdd:cd04980  76 SSVEPEDAAVYYCQQGYTFP 95

Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, 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. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). 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 seem to be functionally identical, and can associate with any of the heavy chains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814   22 IVLTQSIPSLTVSAGERVTISCKSNQNLlwsgnQRYCLVWHQWKPGQTPTPLITWTSDRYSGVPDRFIGSGSVTDFTLTI 101
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSI-----SSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTI 75

                        90       100
                ....*....|....*....|
gi 3355814  102 SSVQAEDVAVYFCQQHLHIP 121
Cdd:cd04980  76 SSVEPEDAAVYYCQQGYTFP 95

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 3355814     29 PSLTVSAGERVTISCksnQNLLWSGNQRYCLVWHQWKPGQTPTPLITWTSDRY--SGVPDRFIGSGSV--TDFTLTISSV 104
Cdd:pfam07686   4 REVTVALGGSVTLPC---TYSSSMSEASTSVYWYRQPPGKGPTFLIAYYSNGSeeGVKKGRFSGRGDPsnGDGSLTIQNL 80

                          90
                  ....*....|.
gi 3355814    105 QAEDVAVYFCQ 115
Cdd:pfam07686  81 TLSDSGTYTCA 91

Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, 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. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). 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 seem to be functionally identical, and can associate with any of the heavy chains.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814   22 IVLTQSIPSLTVSAGERVTISCKSNQNLlwsgnQRYCLVWHQWKPGQTPTPLITWTSDRYSGVPDRFIGSGSVTDFTLTI 101
Cdd:cd04980   1 IVMTQSPASLSVSPGERVTISCKASQSI-----SSNYLAWYQQKPGQAPKLLIYYASTLHSGVPSRFSGSGSGTDFTLTI 75

                        90       100
                ....*....|....*....|
gi 3355814  102 SSVQAEDVAVYFCQQHLHIP 121
Cdd:cd04980  76 SSVEPEDAAVYYCQQGYTFP 95

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 3355814   24 LTQSIPSLTVSAGERVTISCKSNqnllwSGNQRYCLVWHQWKPGQTPTPLITWTSDRYS---GVPDRFIGSGS-VTDFTL 99
Cdd:cd00099   1 VTQSPRSLSVQEGESVTLSCEVS-----SSFSSTYIYWYRQKPGQGPEFLIYLSSSKGKtkgGVPGRFSGSRDgTSSFSL 75

                        90
                ....*....|....*..
gi 3355814  100 TISSVQAEDVAVYFCQQ 116
Cdd:cd00099  76 TISNLQPEDSGTYYCAV 92

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814      29 PSLTVSAGERVTISCKSNQNllwsgnqryclvwhqwkpgqtPTPLITWTSDRYSGV--PDRFIGSGSVTDFTLTISSVQA 106
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGS---------------------PPPEVTWYKQGGKLLaeSGRFSVSRSGSTSTLTISNVTP 60

                   ....*....
gi 3355814     107 EDVAVYFCQ 115
Cdd:smart00410  61 EDSGTYTCA 69

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814      39 VTISCKSNQNllwsGNQRYCLVWHQWKPGQTPTPLITWTSDRY----SGVPDRFIGSGSV--TDFTLTISSVQAEDVAVY 112
Cdd:smart00406   2 VTLSCKFSGS----TFSSYYVSWVRQPPGKGLEWLGYIGSNGSsyyqESYKGRFTISKDTskNDVSLTISNLRVEDTGTY 77

                   ....
gi 3355814     113 FCQQ 116
Cdd:smart00406  78 YCAV 81

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814   25 TQSIPSLTVSAGERVTISCKSNQNllWSgnqRYCLVWHQWKPGQTPTPLITWTSDRYSGVPDRFIGSGSVTD--FTLTIS 102
Cdd:cd07706   3 TQAQPDVSVQVGEEVTLNCRYETS--WT---NYYLFWYKQLPSGEMTFLIRQDSSEQNAKSGRYSVNFQKAQksISLTIS 77

                        90
                ....*....|..
gi 3355814  103 SVQAEDVAVYFC 114
Cdd:cd07706  78 ALQLEDSAKYFC 89

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 3355814   24 LTQSIPSLTVSAGERVTISCK-SNQNLlwsgNQRYcLVWHQWKPGQTPTPLITWTSD----RYSG-VPDRFIGS--GSVT 95
Cdd:cd04982   1 LEQPQLSITREESKSVTISCKvSGIDF----STTY-IHWYRQKPGQALERLLYVSSTsavrKDSGkTKNKFEARkdVGKS 75

                        90
                ....*....|....*....
gi 3355814   96 DFTLTISSVQAEDVAVYFC 114
Cdd:cd04982  76 TSTLTITNLEKEDSATYYC 94

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 3355814   24 LTQSIPSLtVSAGERVTISCKSNQNLLWSgnqrYCLVWHQWKPGQTPTPL-ITWTSDRYSGVPDRFIGSGSVT------D 96
Cdd:cd04981   2 LQESGPGL-VKPGQSLKLSCKASGFTFTS----YGMGWVRQAPGKGLEWIgLIYPGGGDTYYADSFKGRFTITrdtsksT 76

                        90
                ....*....|....*...
gi 3355814   97 FTLTISSVQAEDVAVYFC 114
Cdd:cd04981  77 AYLQLNSLTSEDTAVYYC 94

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor_like-1(FGFRL1); 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 like-1(FGFRL1). FGFRL1 is comprised of a signal peptide, three extracellular Ig-like modules, a transmembrane segment, and a short intracellular domain. FGFRL1 is expressed preferentially in skeletal tissues. Similar to FGF receptors, the expressed protein interacts specifically with heparin and with FGF2. FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*.
gi 3355814   70 PTPLITWTSDRYSGVPDRfIGSGSVTDFTLTISSVQAEDVAVYFCQ 115
Cdd:cd05856  32 PRPDITWLKDNKPLTPPE-IGENKKKKWTLSLKNLKPEDSGKYTCH 76

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

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3355814   23 VLTQSIPSLTVSAGERVTISCKSnqnllwSGNqryclvwhqwkpgqtPTPLITWTSDrysGVP----DRF-IG-----SG 92
Cdd:cd20956   3 VLLETFSEQTLQPGPSVSLKCVA------SGN---------------PLPQITWTLD---GFPipesPRFrVGdyvtsDG 58

                        90       100
                ....*....|....*....|...
gi 3355814   93 SVTDFtLTISSVQAEDVAVYFCQ 115
Cdd:cd20956  59 DVVSY-VNISSVRVEDGGEYTCT 80

Immunoglobulin variable domain (IgV) Cluster of Differentiation (CD) 79B; The members here are composed of the immunoglobulin variable domain (IgV) of the Cluster of Differentiation (CD) 79B (also known as CD79b molecule, immunoglobulin-associated beta (Ig-beta), and B29). The B lymphocyte antigen receptor is a multimeric complex that includes the antigen-specific component, surface immunoglobulin (Ig). Surface Ig non-covalently associates with two other proteins, Ig-alpha and Ig-beta, which are necessary for expression and function of the B-cell antigen receptor. This gene encodes the Ig-beta protein of the B-cell antigen component. Alternatively spliced transcript variants encoding different isoforms have been described. Members of the IgV family 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. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                        10        20
                ....*....|....*....|....*.
gi 3355814   91 SGSVtdFTLTISSVQAEDVAVYFCQQ 116
Cdd:cd16096  54 NGSV--YTLTIQNIQYEDNGIYFCQQ 77