Action of bovine serum albumin on cytochrome c oxidase activity and proton pumping: a role for fatty acids in enzyme function?
Bovine serum albumin (BSA) at micromolar concentrations causes a red shift of the Soret band of bovine cytochrome c oxidase with a slow biphasic time course. It also inhibits the turnover of detergent-isolated enzyme in a similarly slow manner; the progress of this inhibition is halted by palmitate and other fatty acids. The inhibitory bovine serum albumin effect may involve fatty acid depletion from the enzyme. Respiration by cytochrome c oxidase vesicles (proteoliposomes) in the presence of ionophores (uncontrolled) shows only a small inhibition by BSA but preincubation of such vesicles with BSA induces a loss of proton pumping activity. After incubation of BSA-depleted proteoliposomes in the presence of reductant with combinations of fatty acids, pumping activity can be fully restored, suggesting a supportive or even essential role of endogenous fatty acids in H+ translocation by this membranous enzyme.
Sharpe
M
M
Department of Biological Sciences, Brock University, St. Catharines, Ont, Canada.
Perin
I
I
Nicholls
P
P
D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes; D008929:Mitochondria, Heart / Q000201:enzymology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011510:Proteolipids / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013997:Time Factors
D005230:Fatty Acids, Nonesterified; D008081:Liposomes; D011510:Proteolipids; C020485:proteoliposomes; D012710:Serum Albumin, Bovine; D003576:Electron Transport Complex IV