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
                  ....*....|....*....|....*....|....*....|....*....|.
gi 2095549222  16 SLRDNRIELVRASWHELSISVSDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 66
Cdd:cd07701    46 ALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 96

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|.
gi 2095549222  16 SLRDNRIELVRASWHELSISVSDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 66
Cdd:cd07701    46 ALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 96

putative band 4.1 homologues' binding motif;

                           10
                   ....*....|....*....
gi 2095549222  283 LGRYLARHKGTYLTNEAKG 301
Cdd:smart00294   1 MYRYKHRDEGSYHTHEPKG 19

Second immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 - Necl-4; member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 or CADM3), Necl-2 (also known as CADM1), Necl-3 (also known as CADM2) and Necl-4 (also known as CADM4). These nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 through Necl-5). These have an extracellular region containing three Ig-like domains, one transmembrane region, and one cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1 and Necl-2 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues, and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma. Necl-3 has been shown to accumulate in tissues of the central and peripheral nervous system, where it is expressed in ependymal cells and myelinated axons. It is observed at the interface between the axon shaft and the myelin sheath. Necl-4 is expressed on Schwann cells, and plays a key part in initiating peripheral nervous system (PNS) myelination. Necl-4 participates in cell-cell adhesion and is proposed to play a role in tumor suppression.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  66 LGVPEKPQISGFSSPVMEGDLMQLTCKTSGSKPAADIRWFKNDKEIKDVKYLKEEDaNRKTFTVSSTLDFRVDRSDDGVA 145
Cdd:cd05761     1 LGVPEKPVITGFTSPVVEGDEITLTCTTSGSKPAADIRWFKNDKELKGVKEVQESG-AGKTFTVTSTLRFRVDRDDDGVA 79

                          90       100
                  ....*....|....*....|...
gi 2095549222 146 VICRVDHESLNATPQVAMQVLEI 168
Cdd:cd05761    80 VICRVDHESLTSTPKQTQQVLEV 102

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|.
gi 2095549222  16 SLRDNRIELVRASWHELSISVSDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 66
Cdd:cd07701    46 ALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLFTMPVKTSKAYLTVL 96

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-1 (Necl-1); member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-1, Necl-1 (also known as celll adhesion molecule 3 (CADM3), SynCAM2, or IGSF4). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue and is important to the formation of synapses, axon bundles, and myelinated axons.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|
gi 2095549222  16 SLRDNRIELVRASWHELSISVSDVSLSDEGQYTCSLFTMPVKTSKAYLTV 65
Cdd:cd05882    46 ALRDNRIQLVKSTPTELIISISNVQLSDEGEYTCSIFTMPVRTAKATVTV 95

Second immunoglobulin (Ig)-like domain of nectin-like molecule 2 (Necl-2); member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin (Ig)-like domain of nectin-like molecule 2 (Necl-2; also known as cell adhesion molecule 1 (CADM1)). Nectin-like molecules (Necls) have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 through Necl-5). These have an extracellular region containing three Ig-like domains, one transmembrane region, and one cytoplasmic region. Necl-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Ig domains are likely to participate in ligand binding and recognition.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  69 PEKPQISGFSSPVMEGDLMQLTCKTSGSKPAADIRWFKNDKEIKdVKYLKEEDANRkTFTVSSTLDFRVDRSDDGVAVIC 148
Cdd:cd05883     4 PRNLVIDIQKDTAVEGEEIELNCTAMASKPAATIRWFKGNKELT-GKSEVEEWYSR-MFTVTSQLMLKVTKEDDGVPVIC 81

                          90       100
                  ....*....|....*....|
gi 2095549222 149 RVDHESlnATPQVAMQVLEI 168
Cdd:cd05883    82 LVDHPA--VKDLQTQRYLEV 99

Second immunoglobulin (Ig)-like domain of Kirrel (kin of irregular chiasm-like) 3, 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 of Kirrel (kin of irregular chiasm-like) 3 (also known as Neph2). This protein has five Ig-like domains, one transmembrane domain, and a cytoplasmic tail. Included in this group is mammalian Kirrel (Neph1), Kirrel2 (Neph3), and Drosophila RST (irregular chiasm C-roughest) protein. These proteins contain multiple Ig domains, have properties of cell adhesion molecules, and are important in organ development.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  72 PQISGfsSPVME---GDLMQLTCKTSGSKPAADIRWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVIC 148
Cdd:cd05759     2 PVIEG--GPVISlqaGVPYNLTCRARGAKPAAEIIWFRDGEQLEGAVYSKELLKDGKRETTVSTLLITPSDLDTGRTFTC 79

                  ....*..
gi 2095549222 149 RVDHESL 155
Cdd:cd05759    80 RARNEAI 86

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule 2; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-2, Necl-2 (also known as cell adhesion molecule 1 (CADM1), SynCAM1, IGSF4A, Tslc1, sgIGSF, and RA175). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*....
gi 2095549222  17 LRDNRIELVRASWHELSISVSDVSLSDEGQYTCSLFTMPVKTSKAYLTV 65
Cdd:cd05881    46 LKDSRFQLVNFSSSELRVSLTNVSISDEGRYFCQLYTDPPQEAYTTITV 94

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 2095549222  71 KPQISGFSSP--VMEGDLMQLTCKTSGSkPAADIRWFKNDKEIKDVKYLK-EEDANRKTFTVSStldfrVDRSDDGV 144
Cdd:pfam13927   1 KPVITVSPSSvtVREGETVTLTCEATGS-PPPTITWYKNGEPISSGSTRSrSLSGSNSTLTISN-----VTRSDAGT 71

Second immunoglobulin (Ig) domain of Nectin-2 and Nectin-like protein 5, and similar domains; member of the C1-set of the Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig) domain of nectin-2 (also known as poliovirus receptor related protein 2 or Cluster of Differentiation 112 (CD112)), nectin-like protein 5 (CD155), and similar proteins. Nectins and Nectin-like molecules are a family of Ca(2+)-independent immunoglobulin-like transmembrane glycoproteins belonging to the class of adhesion receptors, consisting of nine members (nectins 1 through 4 and nectin-like proteins 1 through 5). 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. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. CD155 is the fifth member in the nectin-like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as Necl-5, or PVR. In contrast to all other family members, CD155 lacks self-adhesion capacity, yet it shares with nectins the feature to interact with other nectins. For instance, CD155 heterophilically trans-interacts with nectin-3, thereby contributing significantly to the establishment of adherens junctions between epithelial cells. This group belongs to the Constant 1 (C1)-set of IgSF domains, which has one beta-sheet that is formed by strands A-B-E-D and the other strands by G-F-C-C'.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  72 PQISGFSSPVMEGDLMQL--TCKTSGSKPAADIRWFKNDKeiKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVICR 149
Cdd:cd07703     1 PKNSAEAQEVQAGGIPVPvaRCVSANGRPPARISWSSTLN--GNANTTQVPGPDSGTVTVTSEYSLVPTPEANGKEVTCK 78

                  ....*..
gi 2095549222 150 VDHESLN 156
Cdd:cd07703    79 VEHETLE 85

CH3 domain (third constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, gamma, and delta chains, and CH4 domain (fourth constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, epsilon, and mu chains; member of the C1-set of I; The members here are composed of the third and fourth immunoglobulin constant domain (IgC) of alpha, delta, gamma and alpha, epsilon, and mu heavy chains, respectively. This domain is found on the Fc fragment. 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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  72 PQISGFSSPVME---GDLMQLTCKTSGSKPAaDI--RWFKNDKEIKDVKYL--KEEDANRKTFTVSSTLdfRVDRSD--D 142
Cdd:cd05768     1 PSVYLLPPPEEElslNETVTLTCLVKGFYPE-DIfvSWLQNGEPLPSADYKttAPVPESDGSFFVYSKL--NVSTADwnS 77

                          90
                  ....*....|...
gi 2095549222 143 GVAVICRVDHESL 155
Cdd:cd05768    78 GDVFSCVVGHEAL 90

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 2095549222  88 QLTCKTSGSkPAADIRWFKNDKEIKDvkylkEEDANRKTFTVSSTLDFR-VDRSDDGVaVICRV 150
Cdd:cd00096     2 TLTCSASGN-PPPTITWYKNGKPLPP-----SSRDSRRSELGNGTLTISnVTLEDSGT-YTCVA 58

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. 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 MuSK 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2095549222  75 SGFSSPVMEGDLMQLTCKTSGSkPAADIRWFKNDKEIkdvkylKEEDANRKTFTVSSTLDFRVDRSDDGVAVICR 149
Cdd:cd20970     8 PSFTVTAREGENATFMCRAEGS-PEPEISWTRNGNLI------IEFNTRYIVRENGTTLTIRNIRRSDMGIYLCI 75

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.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2095549222  81 VMEGDLMQLTCKTSGSkPAADIRWFKNDKEIKDVKY--LKEEDANRKTFTVSstldfRVDRSDDG 143
Cdd:cd05737    13 IMEGKTLNLTCNVWGD-PPPEVSWLKNDQALAFLDHcnLKVEAGRTVYFTIN-----GVSSEDSG 71

putative band 4.1 homologues' binding motif;

                           10
                   ....*....|....*....
gi 2095549222  283 LGRYLARHKGTYLTNEAKG 301
Cdd:smart00294   1 MYRYKHRDEGSYHTHEPKG 19

Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  72 PQISGFSS-PVMEGDLMQLTCKTSGSKPA-ADIRWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDgvaVICR 149
Cdd:cd05770     3 PKVQVYSRfPAENGKPNVLNCYVSGFHPPdIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDE---YACR 79

                  ....*..
gi 2095549222 150 VDHESLN 156
Cdd:cd05770    80 VRHNTLS 86

C-terminal immunoglobulin (Ig)-like domain of 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 M-protein (also known as myomesin-2). M-protein is a structural protein localized to the M-band, a transverse structure in the center of the sarcomere, and is a candidate for M-band bridges. M-protein is modular consisting mainly of repetitive IG-like and fibronectin type III (FnIII) domains and has a muscle-type specific expression pattern. M-protein is present in fast fibers.

                          10        20        30
                  ....*....|....*....|....*....|..
gi 2095549222  81 VMEGDLMQLTCKTSGSkPAADIRWFKNDKEIK 112
Cdd:cd05891    13 IMEGKTLNLTCTVFGN-PDPEVIWFKNDQDIE 43

CH2 domain (second constant Ig domain of the heavy chain) in immunoglobulin mu chain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin constant domain (IgC) of mu heavy chains. This domain is found on the Fc fragment. 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 is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2095549222  71 KPQISGFSSPVMEGDLMQ---LTCKTSGSKPAA-DIRWFKNDKEIKDV--KYLKEEDANRKT-FTVSSTLDfrVDRSD-D 142
Cdd:cd16093     1 PPTVSLHAPSREEFLGNRtatFVCLATGFSPKTiSFKWLRNGKEVTSStgAVVEEPKEDGKTlYSATSFLT--ITESEwK 78

                          90
                  ....*....|....*
gi 2095549222 143 GVAVI-CRVDHESLN 156
Cdd:cd16093    79 SQTEFtCEFKHKGEI 93