A conformational change of the ? subunit indirectly regulates the activity of cyanobacterial F1-ATPase.

ABSTRACT: The central shaft of the catalytic core of ATP synthase, the ? subunit consists of a coiled-coil structure of N- and C-terminal ?-helices, and a globular domain. The ? subunit of cyanobacterial and chloroplast ATP synthase has a unique 30-40-amino acid insertion within the globular domain. We recently prepared the insertion-removed ?(3)?(3)? complex of cyanobacterial ATP synthase (Sunamura, E., Konno, H., Imashimizu-Kobayashi, M., and Hisabori, T. (2010) Plant Cell Physiol. 51, 855-865). Although the insertion is thought to be located in the periphery of the complex and far from catalytic sites, the mutant complex shows a remarkable increase in ATP hydrolysis activity due to a reduced tendency to lapse into ADP inhibition. We postulated that removal of the insertion affects the activity via a conformational change of two central ?-helices in ?. To examine this hypothesis, we prepared a mutant complex that can lock the relative position of two central ?-helices to each other by way of a disulfide bond formation. The mutant obtained showed a significant change in ATP hydrolysis activity caused by this restriction. The highly active locked complex was insensitive to N-dimethyldodecylamine-N-oxide, suggesting that the complex is resistant to ADP inhibition. In addition, the lock affected ? inhibition. In contrast, the change in activity caused by removal of the ? insertion was independent from the conformational restriction of the central axis component. These results imply that the global conformational change of the ? subunit indirectly regulates complex activity by changing both ADP inhibition and ? inhibition.

SUBMITTER: Sunamura E 

PROVIDER: S-EPMC3493913 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature