Innexins

Structure

Innexins have four transmembrane segments (TMSs) and, like the vertebrate connexin gap junction protein, innexin subunits together form a channel (an "innexon") in the plasma membrane of the cell. Two innexons in apposed plasma membranes can form a gap junction channel. Innexons are made from eight subunits, instead of the six subunits of connexons. Structurally, innexins and connexins are very similar, consisting of 4 transmembrane domains, 2 extracellular and 1 intracellular loop, along with intracellular N- and C-terminal tails. Despite this shared topology, the protein families do not share enough sequence similarity to confidently infer common ancestry.