title: A conformational change of the γ subunit indirectly regulates the activity of cyanobacterial F1-ATPase.
abstract: The central shaft of the catalytic core of ATP synthase, the γ subunit consists of a coiled-coil structure of N- and C-terminal α-helices, and a globular domain. The γ 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 α(3)β(3)γ 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 α-helices in γ. To examine this hypothesis, we prepared a mutant complex that can lock the relative position of two central α-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 ε inhibition. In contrast, the change in activity caused by removal of the γ insertion was independent from the conformational restriction of the central axis component. These results imply that the global conformational change of the γ subunit indirectly regulates complex activity by changing both ADP inhibition and ε inhibition.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan.
authors.forename: Ei-Ichiro
authors.initials: E
authors.lastname: Sunamura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Konno
authors.forename: Mari
authors.initials: M
authors.lastname: Imashimizu
authors.forename: Mari
authors.initials: M
authors.lastname: Mochimaru
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
mesh_terms: D025181:ATP Synthetase Complexes / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002417:Cattle; D002736:Chloroplasts / Q000378:metabolism; D000458:Cyanobacteria / Q000201:enzymology* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation; D010084:Oxidation-Reduction; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry*
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D025181:ATP Synthetase Complexes; D006180:Proton-Translocating ATPases