One gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell. A connexon is composed of a hexamer of connexins (By similarity). Interacts with TJP1. Expressed in vascular smooth muscle cells. Found in heart, colon, and artery (at protein level). Found in cerebral cortex, heart, liver, lung, kidney, spleen and testis. Belongs to the connexin family. Delta-type subfamily.