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.