Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74146604   313 PPELLCLASHFFPSEgLEVKWELRGGPggssrkVEGKTWLSTIRHHSDGSVSQSGHLQLPPVTAKQHGVhYVCRVYHSSL 392
Cdd:pfam07654  14 PNTLTCLVTGFYPPD-ITVTWLKNGQE------VTEGVKTTPPSPNSDWTYQLSSYLTVTPSDWESGDE-YTCRVEHEGL 85

Immunoglobulin Constant-1 (C1)-set domain; The members here are composed of C1-set domains, classical Ig-like domains resembling the antibody constant domain. Members of the IgC1 family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and major histocompatibility complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, while the IgC domain is involved in oligomerization and molecular interactions. 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 strands by G, F, C, and C'.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74146604 296 RVSLTPAPVvwAAPGEAPPELLCLASHFFPSEgLEVKWELRGGPGGSSrkvegkTWLSTIRHHSDGSVSQSGHLQLPPVT 375
Cdd:cd00098   1 TVTLLPPSP--EEKGGGKVTLVCLVSGFYPKD-ITVTWLKNGVPLTSG------VSTSSPVEPNDGTYSVTSSLTVPPSD 71

                        90       100
                ....*....|....*....|
gi 74146604 376 AKqHGVHYVCRVYHSSLPAS 395
Cdd:cd00098  72 WD-EGATYTCVVTHESLKSP 90

Immunoglobulin domain of Cluster of Differentiation (CD) 1; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Cluster of Differentiation (CD) 1. CD1 family of transmembrane glycoproteins, are structurally related to the major histocompatibility complex (MHC) proteins and form heterodimers with beta-2-microglobulin. They mediate the presentation of primarily lipid and glycolipid antigens of self or microbial origin to T cells. The human genome contains five CD1 family genes (CD1a, CD1b, CD1c, CD1d, and CD1e) organized in a cluster on chromosome 1. The CD1 family members are thought to differ in their cellular localization and specificity for particular lipid ligands. CD1a localizes to the plasma membrane and to recycling vesicles of the early endocytic system. Alternative splicing results in multiple transcript variants. Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I alpha chain. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells. C1-set Ig domains have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74146604 293 KAPRVSLTPAPvvwaAPGEAPPELLCLASHFFPSEgLEVKWeLRGGpggssRKVEGKTWLSTIRHHSDGSVSQSGHLQLP 372
Cdd:cd21029   1 VKPRVRLSSRP----SPGDGHLQLSCHVTGFYPRP-IEVTW-LRDG-----QEQMDGTQSGGILPNHDGTYQLRKTLDIA 69

                        90       100
                ....*....|....*....|.
gi 74146604 373 PvtAKQHGvhYVCRVYHSSLP 393
Cdd:cd21029  70 P--GEGAG--YSCRVDHSSLK 86

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 74146604 312 APPE----------LLCLASHFFPSEgLEVKWeLRGGPGGSSRKVegKTwlSTIRHHSDGSVSQSGHLQLPpvTAK-QHG 380
Cdd:cd05768   7 PPPEeelslnetvtLTCLVKGFYPED-IFVSW-LQNGEPLPSADY--KT--TAPVPESDGSFFVYSKLNVS--TADwNSG 78

                        90
                ....*....|...
gi 74146604 381 VHYVCRVYHSSLP 393
Cdd:cd05768  79 DVFSCVVGHEALP 91