Tight junction protein ZO-1 also known as Zonula Occludens-1 (ZO-1), is a 220-kD peripheral membrane protein that is encoded by the TJP1gene in humans.[5] It belongs to the family of zonula occludens proteins (ZO-1, ZO-2, and ZO-3), which are tight junction-associated proteins and of which, ZO-1 is the first to be cloned. It was first isolated in 1986 by Stevenson and Goodenough using a monoclonal antibody raised in rodent liver to recognise a 225-kD polypeptide in whole liver homogenates and in tight junction-enriched membrane fractions.[6] It has a role as a scaffold protein which cross-links and anchors Tight Junction (TJ) strand proteins, which are fibril-like structures within the lipid bilayer, to the actin cytoskeleton.[7]