Insight into the Bind-Lock Mechanism of the Yeast Mitochondrial ATP Synthase Inhibitory Peptide
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- 作者：Vincent Corvest ; Claude Sigalat ; Francis Haraux
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：July 24, 2007
- 年：2007
- 卷：46
- 期：29
- 页码：8680 - 8688
- 全文大小：135K
- 年卷期：v.46,no.29(July 24, 2007)
- ISSN：1520-4995
文摘
The mechanism of yeast mitochondrial F1-ATPase inhibition by its regulatory peptide IF1was investigated with the noncatalytic sites frozen by pyrophosphate pretreatment that mimics filling byATP. This allowed for confirmation of the mismatch between catalytic site occupancy and IF1 bindingrate without the kinetic restriction due to slow ATP binding to the noncatalytic sites. These data strengthenthe previously proposed two-step mechanism, where IF1 loose binding is determined by the catalyticstate and IF1 locking is turnover-dependent and competes with IF1 release (Corvest, V., Sigalat, C., Venard,R., Falson, P., Mueller, D. M., and Haraux, F. (2005) J. Biol. Chem. 280, 9927-9936). They alsodemonstrate that noncatalytic sites, which slightly modulate IF1 access to the enzyme, play a minor rolein its binding. It is also shown that loose binding of IF1 to MgADP-loaded F1-ATPase is very slow andthat IF1 binding to ATP-hydrolyzing F1-ATPase decreases nucleotide binding severely in the micromolarrange and moderately in the submillimolar range. Taken together, these observations suggest an outlineof the total inhibition process. During the first catalytic cycle, IF1 loosely binds to a catalytic site withnewly bound ATP and is locked when ATP is hydrolyzed at a second site. During the second cycle,blocking of ATP hydrolysis by IF1 inhibits ATP from becoming entrapped on the third site and, at highATP concentrations, also inhibits ADP release from the second site. This model also provides a clue forunderstanding why IF1 does not bind ATP synthase during ATP synthesis.