K7 a type II cytoskeletal keratin. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. Phosphorylation of keratins at specific sites affects their organization, assembly dynamics, and their interaction with signaling molecules. Specifically expressed in the simple epithelia lining the cavities of the internal organs and in the gland ducts and blood vessels.