Role of Mg2+ in lipid-protein interaction in reconstituted procine heart mitochondrial H+-ATPase.
During reconstitution of pig heart mitochondrial H+-ATPase in soybean phospholipid liposomes by the cholate dialysis method, Mg2+ greatly enhances 32Pi-ATP exchange activity, ATPase activity and the sensitivity to oligomycin of the reconstituted enzyme complex. The effect of Mg2+ on the fluidity of the reconstituted proteoliposomes was measured by means of a fluoursecent probe. 1-anilinonaphthalene ¿e-8-sulfonate, and spin-label probes, 5-nitroxide stearate, 12-nitroxide stearate and 16-nitroxide stearate. A difference in fluidity seems to be localized near the polar faces of the lipid bilayers of the reconstituted proteolipsomes. Fluidity was less in the presence of Mg2+ than it is absence. The conformations of the Mg2+-containing proteoliposomes was higher. We postulate that Mg2+ may play a role in altering the fluidity of the proteoliposomes, which would favor the formation of a conformation of the reconstituted H+-ATPase with higher activity.
D000251:Adenosine Triphosphatases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008081:Liposomes; D008274:Magnesium / Q000494:pharmacology*; D008929:Mitochondria, Heart / Q000201:enzymology*; D010743:Phospholipids / Q000494:pharmacology; D006180:Proton-Translocating ATPases; D013025:Glycine max; D013552:Swine
D008081:Liposomes; D010743:Phospholipids; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; D008274:Magnesium