Activation of Mg-ATP hydrolysis in isolated Rhodospirillum rubrum H+-ATPase.
The effects of lauryl dimethylamine oxide on the Rhodospirillum rubrum H+-ATPase have been studied. This detergent activates Mg2+-dependent ATP hydrolysis in the isolated R. rubrum F0-F1 34-fold, whereas the Ca2+-ATPase activity is only slightly modified. ATPase activation by lauryl dimethylamine oxide enhances the effect on ATP hydrolysis exerted by free Mg2+ ions. Concentrations of free Mg2+ in the range of 0.025 mM favor activation while higher concentrations inhibit ATPase activity by approximately 70%. Steady-state kinetic analysis shows that lauryl dimethylamine oxide induces a complex kinetic behavior for Mg-ATP in the chromatophores, similar to the untreated F0-F1 complex. The initial rate value for Mg-ATP unisite catalysis was found to be 6.3 times higher (3.5 X 10(-3) mol Pi per mol R. rubrum F0-F1 per second) in the presence than in the absence of detergent, where the initial rate was 5.5 X 10(-4) mol Pi per mol R. rubrum F0-F1 per second. These experiments show that lauryl dimethylamine oxide shifts the cation requirement for ATP-hydrolysis of the isolated R. rubrum H+-ATPase from Ca2+ to Mg2+ and that it activates both multisite and unisite catalysis. Results are discussed in relation to the possibility of a regulatory role by Mg2+ ions on ATP hydrolysis expressed through subunit interactions.
D000255:Adenosine Triphosphate / Q000378:metabolism*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004123:Dimethylamines / Q000494:pharmacology; D006868:Hydrolysis; D007700:Kinetics; D006180:Proton-Translocating ATPases / Q000302:isolation & purification / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology*
D003902:Detergents; D004123:Dimethylamines; C014518:dodecyldimethylamine oxide; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D006180:Proton-Translocating ATPases; D000252:Calcium-Transporting ATPases