The protein encoded by this gene is a member of the membrane-associated guanylate kinase-like (MAGUK) protein family which is characterized by members having multiple PDZ domains, a single SH3 domain, and a single guanylate kinase-like (GUK)-domain. In addition, members of the zonula occludens protein subfamily have an acidic domain, a basic arginine-rich region, and a proline-rich domain. The protein encoded by this gene plays a role in the linkage between the actin cytoskeleton and tight-junctions and also sequesters cyclin D1 at tight junctions during mitosis. Alternative splicing results in multiple transcript variants encoding distinct isoforms. This gene has a partial pseudogene on chromosome 1.