Figure 2.

Assembly of Pannexin channels in the plasma membrane of eukaryotes. (a) Pannexins insert with four transmembrane domains (lighter blue; top panel) in the plasma membrane of cells. The second extraplasmic loop comprises an N-glycosylation site at residue N254 (black appendage). The pannexin hexamer forms the transmembrane channel (blue; middle panel). The glycosylation is thought to prevent the formation of intercellular pannexin gap junctions (lower panel). Schematic drawings are not to scale. (b) Pannexins do not assemble in gap junction-like structured plaques upon over-expression in HEK 293-cells [51]. Shown are freeze-fractured membranes of Panx1-EYFP-transfected cells after immunolabeling using anti-GFP antibodies, detected by 12 nm colloidal gold-coupled secondary antibodies (black dots). Scale bar 100 nm.