Figure 1.

Assembly of connexin proteins to form gap junctions within the plasma membrane of eukaryotes. (a) Connexin proteins insert with four transmembrane domains (upper panel; light green) in the plasma membrane of cells. Six connexins oligomerize and form a transmembrane channel (middle panel; hemichannel in green, a single connexin protein is highlighted in light green). Hemichannel-containing membranes of adjacent cells converge to 2 nm, forming an intercellular gap junction. Schematic drawings are not to scale. (b) Connexin-gap junction, here shown in the membrane of cultured murine primary astrocytes, display as hexagonally structured plaque in freeze-fracture replicas with particle-rich areas (P-face, P) and areas with pits (E-face, E). Black dots represent Cx43-immunosignal after labeling with 12 nm colloidal gold-coupled secondary antibodies. Scale bar 100 nm.