Summary: Class I Histocompatibility antigen, domains alpha 1 and 2
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Class I Histocompatibility antigen, domains alpha 1 and 2 Provide feedback
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Madden DR, Gorga JC, Strominger JL, Wiley DC. , Cell 1992;70:1035-1048.: The three-dimensional structure of HLA-B27 at 2.1 A resolution suggests a general mechanism for tight peptide binding to MHC. PUBMED:1525820 EPMC:1525820
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001039
Major Histocompatibility Complex (MHC) glycoproteins are heterodimeric cell surface receptors that function to present antigen peptide fragments to T cells responsible for cell-mediated immune responses. MHC molecules can be subdivided into two groups on the basis of structure and function: class I molecules present intracellular antigen peptide fragments (~10 amino acids) on the surface of the host cells to cytotoxic T cells; class II molecules present exogenously derived antigenic peptides (~15 amino acids) to helper T cells. MHC class I and II molecules are assembled and loaded with their peptide ligands via different mechanisms. However, both present peptide fragments rather than entire proteins to T cells, and are required to mount an immune response.
Class I MHC glycoproteins are expressed on the surface of all somatic nucleated cells, with the exception of neurons. MHC class I receptors present peptide antigens that are synthesised in the cytoplasm, which includes self-peptides (presented for self-tolerance) as well as foreign peptides (such as viral proteins). These antigens are generated from degraded protein fragments that are transported to the endoplasmic reticulum by TAP proteins (transporter of antigenic peptides), where they can bind MHC I molecules, before being transported to the cell surface via the Golgi apparatus [PUBMED:9485452, PUBMED:15526153]. MHC class I receptors display antigens for recognition by cytotoxic T cells, which have the ability to destroy viral-infected or malignant (surfeit of self-peptides) cells.
MHC class I molecules are comprised of two chains: a MHC alpha chain (heavy chain), and a beta2-microglobulin chain (light chain), where only the alpha chain spans the membrane. The alpha chain has three extracellular domains (alpha 1-3, with alpha1 being at the N terminus), a transmembrane region and a C-terminal cytoplasmic tail. The soluble extracellular beta-2 microglobulin chain associates primarily with the alpha-3 domain and is necessary for MHC stability. The alpha1 and alpha2 domains of the alpha chain are referred to as the recognition region, because the peptide antigen binds in a deep groove between these two domains.
This entry represents the alpha chain domains alpha1 and alpha2 that make up this recognition region (the alpha3 domain is represented by (INTERPRO).
More information about these proteins can be found at Protein of the Month: MHC [PUBMED:].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||membrane (GO:0016020)|
|MHC class I protein complex (GO:0042612)|
|Biological process||antigen processing and presentation (GO:0019882)|
|immune response (GO:0006955)|
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|Number in seed:||25|
|Number in full:||25261|
|Average length of the domain:||155.50 aa|
|Average identity of full alignment:||62 %|
|Average coverage of the sequence by the domain:||74.51 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||13|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the MHC_I domain has been found. There are 732 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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