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J Biol Chem. 2008 Jul 25;283(30):20789-96. doi: 10.1074/jbc.M801276200. Epub 2008 May 20.

ATP hydrolysis and synthesis of a rotary motor V-ATPase from Thermus thermophilus.

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  • 1Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Japan.

Abstract

Vacuolar-type H(+)-ATPase (V-ATPase) catalyzes ATP synthesis and hydrolysis coupled with proton translocation across membranes via a rotary motor mechanism. Here we report biochemical and biophysical catalytic properties of V-ATPase from Thermus thermophilus. ATP hydrolysis of V-ATPase was severely inhibited by entrapment of Mg-ADP in the catalytic site. In contrast, the enzyme was very active for ATP synthesis (approximately 70 s(-1)) with the K(m) values for ADP and phosphate being 4.7 +/- 0.5 and 460 +/- 30 microm, respectively. Single molecule observation showed V-ATPase rotated in a 120 degrees stepwise manner, and analysis of dwelling time allowed the binding rate constant k(on) for ATP to be estimated ( approximately 1.1 x 10(6) m(-1) s(-1)), which was much lower than the k(on) (= V(max)/K(m)) for ADP ( approximately 1.4 x 10(7) m(-1) s(-1)). The slower k(on)(ATP) than k(on)(ADP) and strong Mg-ADP inhibition may contribute to prevent wasteful consumption of ATP under in vivo conditions when the proton motive force collapses.

PMID:
18492667
[PubMed - indexed for MEDLINE]
PMCID:
PMC3258951
Free PMC Article
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