Fig. 1

The assembly of connexins into gap junctions. a The topology of a gap junction protein (connexin). A connexin contains a cytoplasmic N-terminus (AT), four transmembrane domains, two extracellular loops (EL1 and EL2), a cytoplasmic loop, and a cytoplasmic C-terminal tail (CT). b Connexins assemble into hexamers to form a hemichannel. c Docking of two hemichannels from two neighboring cells forms a gap junction. The exchange of small (< 1 kDa) molecules mediated by gap junctions is called gap junctional intercellular communication (GJIC)