Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Midori-Ku, Yokohama, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Midori-Ku, Yokohama, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
J Biol Chem. 2022 Nov;298(11):102541. doi: 10.1016/j.jbc.2022.102541. Epub 2022 Sep 27.
Chloroplast FF-ATP synthase (CFCF) uses an electrochemical gradient of protons across the thylakoid membrane (ΔμH) as an energy source in the ATP synthesis reaction. CFCF activity is regulated by the redox state of a Cys pair on its central axis, that is, the γ subunit (CF-γ). When the ΔμH is formed by the photosynthetic electron transfer chain under light conditions, CF-γ is reduced by thioredoxin (Trx), and the entire CFCF enzyme is activated. The redox regulation of CFCF is a key mechanism underlying the control of ATP synthesis under light conditions. In contrast, the oxidative deactivation process involving CFCF has not been clarified. In the present study, we analyzed the oxidation of CF-γ by two physiological oxidants in the chloroplast, namely the proteins Trx-like 2 and atypical Cys-His-rich Trx. Using the thylakoid membrane containing the reduced form of CFCF, we were able to assess the CF-γ oxidation ability of these Trx-like proteins. Our kinetic analysis indicated that these proteins oxidized CF-γ with a higher efficiency than that achieved by a chemical oxidant and typical chloroplast Trxs. Additionally, the CF-γ oxidation rate due to Trx-like proteins and the affinity between them were changed markedly when ΔμH formation across the thylakoid membrane was manipulated artificially. Collectively, these results indicate that the formation status of the ΔμH controls the redox regulation of CFCF to prevent energetic disadvantages in plants.
叶绿体 FF-ATP 合酶（CFCF）利用跨类囊体膜的质子电化学梯度（ΔμH）作为 ATP 合成反应的能量来源。CFCF 的活性受其中心轴上一对半胱氨酸残基（CF-γ）的氧化还原状态调节。当 ΔμH 在光照条件下由光合电子传递链形成时，CF-γ被硫氧还蛋白（Trx）还原，整个 CFCF 酶被激活。CFCF 的氧化还原调节是光照条件下控制 ATP 合成的关键机制。相比之下，涉及 CFCF 的氧化失活过程尚未得到阐明。在本研究中，我们分析了叶绿体中两种生理氧化剂对 CF-γ的氧化作用，即 Trx 样蛋白 2 和非典型的富含半胱氨酸-组氨酸的 Trx。使用含有 CFCF 还原形式的类囊体膜，我们能够评估这些 Trx 样蛋白的 CF-γ氧化能力。我们的动力学分析表明，这些蛋白对 CF-γ的氧化效率高于化学氧化剂和典型的叶绿体 Trxs。此外，当人为操纵跨类囊体膜的 ΔμH 形成时，Trx 样蛋白的 CF-γ氧化速率及其亲和力发生显著变化。综上所述，这些结果表明 ΔμH 的形成状态控制着 CFCF 的氧化还原调节，以防止植物中的能量劣势。
