This gene encodes an integral membrane protein that is required for cytokine-induced regulation of the tight junction paracellular permeability barrier. Mutations in this gene are thought to be a cause of band-like calcification with simplified gyration and polymicrogyria (BLC-PMG), an autosomal recessive neurologic disorder that is also known as pseudo-TORCH syndrome. Alternative splicing results in multiple transcript variants. A related pseudogene is present 1.5 Mb downstream on the q arm of chromosome 5. [provided by RefSeq, Apr 2011]

OCLN gene is located on the long arm of chromosome 5. With its nine exons, this gene spans a length of about 53 kb. At least eight splice variants of this gene are known; only three of them are known to be protein coding. The gene is partially duplicated in a pseudogene form in another region on chromosome 5q, telomeric to the location of the full-length gene.

The Occludin protein is made up of 522 amino acids, and has a size of about 60 kDa. The protein likely spans the plasma membrane four times, forming two extracellular loops which might be involved in the regulation of paracellular permeability. Both the C- and N-terminals lie within the cytoplasm; the C-terminal is thought to play a role in the interaction of the protein with other cytoplasmic proteins of the junctional plaque. Occludin contains the MARVEL domain, which is a conserved domain involved in membrane apposition events, as well a large intracellular protein (ELL) domain. Interestingly, the Hepatitis C Virus uses the MARVEL domain to make its entry into human cells. The Occludin pseudogene mentioned earlier lacks the MARVEL domain, but contains the ELL domain.