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A co-receptor is a cell surface receptor that binds a signalling molecule in addition to a primary receptor in order to facilitate ligand recognition and initiate biological processes, such as entry of a pathogen into a host cell. ==Properties== The term co-receptor is prominent in literature regarding signal transduction, the process by which external stimuli regulate internal cellular functioning.〔Gomperts, BD.; Kramer, IM. Tatham, PER. (2002). Signal transduction. Academic Press. ISBN 0-12-289631-9 ISBN.〕 The key to optimal cellular functioning is maintained by possessing specific machinery that can carry out tasks efficiently and effectively. Specifically, the process through which intermolecular reactions forward and amplify extracellular signals across the cell surface has developed to occur by two mechanisms. First, cell surface receptors can directly transduce signals by possessing both serine and threonine or simply serine in the cytoplasmic domain. They can also transmit signals through adaptor molecules through their cytoplasmic domain which bind to signalling motifs. Secondly, certain surface receptors lacking a cytoplasmic domain can transduce signals through ligand binding. Once the surface receptor binds the ligand it forms a complex with a corresponding surface receptor to regulate signalling.〔Kirkbridge, K.C., Ray, B.N., Blobe, G.C. (2005). "Cell-surface co-receptors: emerging roles in signaling and human disease". Trends Biochem. Sci. 30 (11): 611–21. . PMID 16185874.〕 These categories of cell surface receptors are prominently referred to as co-receptors. Co-receptors are also referred to as accessory receptors, especially in the fields of biomedical research and immunology.〔 Co-receptors are proteins that maintain a three-dimensional structure. The large extracellular domains make up approximately 76–100% of the receptor.〔 The motifs that make up the large extracellular domains participate in ligand binding and complex formation.〔Guo D, Jia Q. et al (1995). "Vascular endothelial cell growth factor promotes tyrosine phosphorylation of mediators of signal transduction that contain SH2 domains and association with endothelial cell proliferation". J Biol Chem 270 (12): 6729–6733.〕 The motifs can include glycosaminoglycans, EGF repeats, cysteine residues or ZP-1 domains.〔 The variety of motifs leads to co-receptors being able to interact with two to nine different ligands, which themselves can also interact with a number of different co-receptors.〔 Most co-receptors lack a cytoplasmic domain and tend to be GPI-anchored, though a few receptors have been identified which contain short cytoplasmic domains that lack intrinsic kinase activity.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Co-receptor」の詳細全文を読む スポンサード リンク
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