Junctional channels are an assembly of two docked connexons on adjacent cells that permits direct communication of the cytoplasm in the two cells as shown below. Proteins associated with GJs such as catenins (Wu et al., 2003, Shaw et al., 2007) and L-CAM (Musil et al., 1990) might be required for connexon docking. Docking occurs through a tight interaction of the extracellular loops (Unger et al., 1999; Sosinsky and Nicholson, 2005). Intramolecular disulfide bridges between the two extracellular loops (E1 and E2) of connexin polypeptides are important for the correct three-dimensional structure of the extracellular loops (Foote et al., 1998)