Background:
Occludin is an integral membrane protein located at the tight junction. It is a tetraspanin protein with four transmembrane domains, intracellular N and C termini and two extracellular loops. Occludin plays a role in the formation and regulation of the tight junction paracellular permeability barrier. Occludin can exist in different isoforms, owing to modifications at the posttranscriptional and posttranslational levels, the monomeric occludin migrates as 53-65 kDa on SDS-PAGE (PMID: 22083955; 19457074).