| Co-Investigator(Kenkyū-buntansha) |
OKA Toshihiko Osaka Univ., ISIR-SANKEN,Research Associate, 産業科学研究所, 助手 (40263321)
IWAMOTO Atsuko Osaka Univ.ISIR-SANKEN,Research Assistant, 産業科学研究所, 教務職員 (70252715)
MORIYAMA Yoshinori Osaka Univ., ISIR-SANKEN,Research Associate, 産業科学研究所, 助手 (10150658)
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| Research Abstract |
The ATP synthase (FoFl, H^+ATPase) catalyzes ATP synthesis of hydrolysis coupling with proton translocation. Escherichia coli enzyme is similar to those found in inner mitochondrial or chloroplast thylakoid membranes, and has contributed greatly to the understanding of this complicated enzyme. The ctalytic site of the enzyme is in the beta subunit or at the interface between the alpha and beta subunits of the membrane extrinsic Fl sector. The proton pathway is fomed from the a b, and c subunit of the membrane intrinsic Fo sector. The gamma, delta, and epsilon subunits of the Fl are required funcionally and structrually to connect the catalyic subunits to the Fo sector. The mechanism of ATP hydrolysis can be studied using purified (Fl-ATPase).
In this project we defined, by mutational analysis of the E.Coli enzyme, the catalytic site in the beta subunit and the active role (s) of the gamma subunit in the energy coupling between the chemical (ATP synthesis/hydrolysis) and osmotic reaction (proton translocation).
Results obtained for the beta subunit catalytic site were : (1) betaLys-155 and betaThr-156 in the glycine-rich sequence (Cly-Cly-Ala-Cly-Val-Cly-Lys-Thr, residues 149-156) are essential for catalysis ;
(2) betaClu 181 and betaArg-182 in the conserved GER sequence are essential catalytic residues ;
(3) betaCly-149 is close to betaCly-172, betaSer-174, betaClu-192 and betaVal-198. From these results, amodel of the catalytic site is proposed that is consistent with the inhibitor sensitvities of the mutant enzmes. This model is consistent with that obtained from recent X ray structure of Fl. Genetic studies suggested that the gamma subunit plays a role in regulation energy coupling (coupling between catalysis and proton transport) : gammaMet-23, gammaArg-242, and the region between gammaCln-269 and gammaVal-280 are close to each other and interract for efficient energy coupling.
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