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Structure of the MHC Class I Homolog MICBStructure of the MHC Class I Homolog MICB
Structural highlights
DiseaseMICB_HUMAN Genetic variations in MICA are a cause of susceptibility to rheumatoid arthritis (RA) [MIM:180300. It is a systemic inflammatory disease with autoimmune features and a complex genetic component. It primarily affects the joints and is characterized by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Note=The MICB*004 allele is associated with rheumatoid arthritis. Note=Genetic variation in MICB is associated with cytomegalovirus and herpes simplex virus I seropositivity and this may be associated with schizophrenia risk. FunctionMICB_HUMAN Seems to have no role in antigen presentation. Acts as a stress-induced self-antigen that is recognized by gamma delta T cells. Ligand for the KLRK1/NKG2D receptor. Binding to KLRK1 leads to cell lysis.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMIC-A and MIC-B are distant MHC class I homologs that serve as stress-inducible Ags on epithelial and epithelially derived cells. They are ligands for the widely expressed activating immunoreceptor NKG2D. To define the structural and functional consequences of sequence differences between MIC-A and MIC-B and between alleles of MIC-A and alleles of MIC-B, we determined the crystal structure of one allele of human MIC-B. Comparisons between the two previously reported MIC-A crystal structures and the MIC-B crystal structure show that, as expected, MIC-B is very similar in structure to MIC-A and likely interacts with NKG2D in an analogous manner. The interdomain flexibility observed in the MIC-A structures, a feature unique to MIC proteins among MHC class I proteins and homologs, is also displayed by MIC-B, with an interdomain relationship intermediate between the two examples of MIC-A structures. Mapping sequence variations onto the structures of MIC-A and MIC-B reveals patterns completely distinct from those displayed by classical MHC class I proteins, with a number of substitutions falling on positions likely to affect interactions with NKG2D, but with other positions lying distant from the NKG2D binding sites or buried within the core of the proteins. Structural studies of allelic diversity of the MHC class I homolog MIC-B, a stress-inducible ligand for the activating immunoreceptor NKG2D.,Holmes MA, Li P, Petersdorf EW, Strong RK J Immunol. 2002 Aug 1;169(3):1395-400. PMID:12133964[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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