Voltage dependence of liver gap-junction channels reconstituted into liposomes and incorporated into planar bilayers.
The voltage dependence of rat liver gap junctions was investigated using non-denaturing solubilization and reconstitution of gap-junction protein into proteoliposomes in controlled conditions of connexon aggregation. The presence of liver connexin 32 in reconstituted proteoliposomes was checked with specific antibodies. The proteoliposomes were inserted into planar lipid bilayers by fusion. The single-channel conductance was voltage independent, and its magnitude was 700-1900 pS in 1 M NaCl, as expected from other reports, assuming that conductance is linear with ion activity. The channels were open at zero voltage and completely closed above 40 mV in either direction. This steep voltage dependence corresponded to an open/closed-state voltage difference of 19 mV and to 3.5 gating charges moving through the field. When several channels were inserted into the bilayer, a large fraction of the membrane conductance became voltage insensitive. These results show that the isolated channel units are highly voltage dependent and are consistent with the assumption that aggregated connexons interact through links which prevent voltage-sensitive conformational changes.
Mazet
J L
JL
Laboratoire de Physiologie Cellulaire, URA 1121, Université Paris-Sud, France.
Jarry
T
T
Gros
D
D
Mazet
F
F
D000595:Amino Acid Sequence; D000818:Animals; D017630:Connexins; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000378:metabolism*; D015640:Ion Channel Gating; D008051:Lipid Bilayers; D008081:Liposomes; D008099:Liver / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011510:Proteolipids / Q000378:metabolism; D051381:Rats
D017630:Connexins; D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins; D011510:Proteolipids; C020485:proteoliposomes