Occludin is a protein that in humans is encoded by the OCLNgene. Occludin is a 65-kDa (522-amino acid polypeptide -human) integral plasma-membrane protein located at the tight junctions, described for the first time in 1993 by Shoichiro Tsukita. Together with the Claudin group of proteins, it is the main component of the tight junctions.
According to its overall hydrophilicity, occludin appears to span the plasma membrane four times, forming two extracellular loops and exposing its NH2 and COOH terminus to the cytosol. Interaction of occludin with several cytoplasmic proteins of the junctional plaque has been found to occur via its COOH terminus, while the extracellular loops are thought to be involved in the regulation of paracellular permeability and cell adhesion. Phosphorylation/dephosphorylation plays a major role in regulation of occludin and tight junctions.
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Itoh M, Morita K, Tsukita S (1999). "Characterization of ZO-2 as a MAGUK family member associated with tight as well as adherens junctions with a binding affinity to occludin and alpha catenin". J. Biol. Chem.274 (9): 5981–5986. doi:10.1074/jbc.274.9.5981. PMID10026224.
Wittchen ES, Haskins J, Stevenson BR (2000). "Protein interactions at the tight junction. Actin has multiple binding partners, and ZO-1 forms independent complexes with ZO-2 and ZO-3". J. Biol. Chem.274 (49): 35179–35185. doi:10.1074/jbc.274.49.35179. PMID10575001.
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