Subunit structure of the connexons in hepatocyte gap junctions.
The connexons in the mouse hepatocyte gap junctions consistently reveal a subunit structure in rotary shadowed replicas of quick frozen freeze-fractured material. Quick freezing eliminates treatment of the material with chemical fixatives and cryoprotectants and hence captures the structures in their native state. Previous biophysical studies have indicated that the connexon in hepatocyte gap junction is composed of 6 subunits. In rotary shadowed replicas, some connexons have 6 subunits while the rest reveal less than 6 subunits. Visualization of less than 6 subunits may be due to local variations in the angle of shadowing because of an uneven plane of fracturing and/or breaking of some of the subunits during freeze-fracturing. Markham's rotation technique reveals that some connexons have a hexameric symmetry while others approach a tetrameric symmetry. Using models of connexons and tilting experiments with the replicas it is shown that these apparent deviations from the hexameric symmetry result from inclination of the fractured face relative to the plane of viewing.
D000818:Animals; D002450:Cell Communication; D055598:Chemical Phenomena; D002621:Chemistry; D005614:Freeze Fracturing; D008099:Liver / Q000166:cytology*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D014961:X-Ray Diffraction
D008565:Membrane Proteins