Journal Article

Binding of an Intrinsic ATPase Inhibitor to the F<sub>1</sub>FoATPPase in Phosphorylating Conditions of Yeast Mitochondria

Hiroyuki Iwatsuki, Yi-Min Lu, Kou Yamaguchi, Naoki Icbikawa and Tadao Hashimoto

in The Journal of Biochemistry

Published on behalf of The Japanese Biochemical Society

Volume 128, issue 4, pages 553-559
Published in print October 2000 | ISSN: 0021-924X
Published online October 2000 | e-ISSN: 1756-2651 | DOI:
Binding of an Intrinsic ATPase Inhibitor to the F1FoATPPase in Phosphorylating Conditions of Yeast Mitochondria

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Yeast mitochondrial ATP synthase has three regulatory proteins; ATPase inhibitor, 9K protein, and 15K protein. A mutant yeast lacking these three regulatory factors was constructed by gene disruption. Rates of ATP synthesis of both wild-type and the mutant yeast mitochondria decreased with decrease of respiration, while their membrane potential was maintained at 170–160 mV under various respiration rates. When mitochondrial respiration was blocked by antimycin A, the membrane potential of both types of mitochondria was maintained at about 160 mV by ATP hydrolysis. ATP hydro-lyzing activity of F1FoATPase solubilized from normal mitochondria decreased in proportion to the rate of ATP synthesis, while the activity of the mutant F,FoATPase was constant regardless of changes in the rate of phosphorylation. These observations strongly suggest that F1FoATPase in the phosphorylating mitochondria is a mixture of two types of enzyme, phosphorylating and non-phosphorylatdng enzymes, whose ratio is determined by the rate of respiration and that the ATPase inhibitor binds preferentially to the non-phosphorylating enzyme.

Keywords: ATPase inhibitor; ATP synthesis; F1FoATPase; localized proton theory; membrane potential

Journal Article.  0 words. 

Subjects: Biochemistry

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