Regulation of the Pi-ATP exchange and hydrolytic reactions in F0-F1 reconstituted liposomes.
The regulation of ATP hydrolysis and Pi-ATP exchange reactions by ATP, ADP, Mg2+, and phosphate was studied in liposomes containing F0-F1 obtained from bovine heart submitochondrial particles by solubilization with lauryl dimethylamino oxide as described previously (Dreyfus, G., Celis, H., and Ramirez, J. (1984) Anal. Biochem. 142, 215-220). A simultaneous analysis of ATP hydrolysis and the Pi-ATP exchange reactions showed that the ratio of hydrolysis/exchange is close to one when the ATP concentration is in the lower micromolar range. In this preparation ADP stimulates the Pi-ATP exchange reaction and depresses ATP hydrolysis. The exchange reaction is almost abolished when ADP is removed from the medium by an ATP-regenerating system. Mg2+ in millimolar concentrations stimulates Pi-ATP exchange, and at the same time decreases ATP hydrolysis; accordingly, the hydrolysis/exchange ratio depends on the concentration of Mg2+. Inorganic phosphate also controls this ratio, a lower ratio being observed at high phosphate concentrations. The Pi-ATP exchange reaction, but not ATP hydrolysis, depends on the concentration of medium phosphate. These results indicate that the kinetic characteristics of this F0-F1 preparation are modified by Mg2+, ATP, and phosphate.
Dreyfus
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D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D006868:Hydrolysis; D007700:Kinetics; D008081:Liposomes; D008274:Magnesium / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000201:enzymology*; D010710:Phosphates / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*
D008081:Liposomes; D010710:Phosphates; D011510:Proteolipids; C020485:proteoliposomes; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D008274:Magnesium