Institute of Basic Biological Problems, FRC PSCBR RAS, Pushchino, Moscow Region, Russia, 142290.
Department of Chemistry "Giacomo Ciamician", University of Bologna, Via F. Selmi 2, 40126, Bologna, Italy.
Photosynth Res. 2019 Aug;141(2):165-179. doi: 10.1007/s11120-019-00617-w. Epub 2019 Jan 30.
In the present study, we have investigated the effect of hydroxyectoine (Ect-OH), a heterocyclic amino acid, on oxygen evolution in photosystem II (PS II) membrane fragments and on photoinhibition of Mn-depleted PS II (apo-WOC-PS II) preparations. The degree of photoinhibition of apo-WOC-PS II preparations was estimated by the loss of the capability of exogenous electron donor (sodium ascorbate) to restore the amplitude of light-induced changes of chlorophyll fluorescence yield (∆F). It was found that Ect-OH (i) stimulates the oxygen-evolving activity of PS II, (ii) accelerates the electron transfer from exogenous electron donors (K[Fe(CN)], DPC, TMPD, Fe, and Mn) to the reaction center of apo-WOC-PS II, (iii) enhances the protective effect of exogenous electron donors against donor-side photoinhibition of apo-WOC-PS II preparations. It is assumed that Ect-OH can serve as an artificial electron donor for apo-WOC-PS II, which does not directly interact with either the donor or acceptor side of the reaction center. We suggest that the protein conformation in the presence of Ect-OH, which affects the extent of hydration, becomes favorable for accepting electrons from exogenous donors. To our knowledge, this is the first study dealing with redox activity of Ect-OH towards photosynthetic pigment-protein complexes.
在本研究中，我们研究了羟基乙四唑（Ect-OH），一种杂环氨基酸，对光合系统 II（PS II）膜片段中氧气的释放以及锰耗竭的 PS II（apo-WOC-PS II）制剂的光抑制的影响。apo-WOC-PS II 制剂的光抑制程度通过外源电子供体（抗坏血酸钠）恢复叶绿素荧光产额（∆F）诱导的光变化幅度的能力丧失来估计。结果发现，Ect-OH（i）刺激 PS II 的氧气释放活性，（ii）加速外源电子供体（K[Fe（CN）]，DPC，TMPD，Fe 和 Mn）向 apo-WOC-PS II 的反应中心的电子转移，（iii）增强外源电子供体对 apo-WOC-PS II 制剂供体侧光抑制的保护作用。假设 Ect-OH 可以作为 apo-WOC-PS II 的人工电子供体，它不会直接与反应中心的供体或受体侧相互作用。我们认为，存在 Ect-OH 时的蛋白质构象影响水合程度，有利于从外源供体接受电子。据我们所知，这是首次研究 Ect-OH 对光合色素-蛋白复合物的氧化还原活性。
