Mechanism of Energy Coupling between Catalysis (ATP Synthesis and Hydrolysis) and H^+ Transport in ATP Synthase

ATP合酶（FoF 1，H^+ATPase）催化ATP的水解合成，并伴有质子转运.大肠杆菌中的酶与线粒体或叶绿体类囊体膜中的酶相似，对理解这种复杂的酶有很大贡献。酶的催化位点在β亚基中或在膜外源性Fl区段的α和β亚基之间的界面处。质子通路由膜内Fo区的a B和c亚基形成。Fl的γ、δ和γ亚基在功能上和结构上需要将催化亚基连接到Fo区段。ATP水解的机理可以用纯化的在这个项目中，我们通过对大肠杆菌酶的突变分析，确定了β亚基中的催化位点和γ亚基在化学物质与酶之间的能量耦合中的活性作用。（ATP合成/水解）和渗透反应对于β亚基催化位点获得的结果是：（1）富含甘氨酸序列中的betaLys-155和betaThr-156（Cly-Cly-Ala-Cly-Val-Cly-Lys-Thr，残基149-156）是催化所必需的;（2）保守的格尔序列中的β Clu 181和β Arg-182是催化所必需的残基;（3）betaCly-149与betaCly-172、betaSer-174、betaClu-192和betaVal-198接近。根据这些结果，提出了与突变酶的抑制剂敏感性一致的催化位点模型。遗传学研究表明，γ亚基在调节能量耦合（催化与质子运输之间的耦合）中起作用：γ Met-23、γ Arg-242以及γ Cln-269和γ Val-280之间的区域相互靠近，相互作用以实现有效的能量耦合。

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.