Probing substrate water access through the O1 channel of Photosystem II by single site mutations and membrane inlet mass spectrometry.

IF 2.9 3区 生物学 Q2 PLANT SCIENCES
A Orkun Aydin, Casper de Lichtenberg, Feiyan Liang, Jack Forsman, André T Graça, Petko Chernev, Shaochun Zhu, André Mateus, Ann Magnuson, Mun Hon Cheah, Wolfgang P Schröder, Felix Ho, Peter Lindblad, Richard J Debus, Fikret Mamedov, Johannes Messinger
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Abstract

Light-driven water oxidation by photosystem II sustains life on Earth by providing the electrons and protons for the reduction of CO2 to carbohydrates and the molecular oxygen we breathe. The inorganic core of the oxygen evolving complex is made of the earth-abundant elements manganese, calcium and oxygen (Mn4CaO5 cluster), and is situated in a binding pocket that is connected to the aqueous surrounding via water-filled channels that allow water intake and proton egress. Recent serial crystallography and infrared spectroscopy studies performed with PSII isolated from Thermosynechococcus vestitus (T. vestitus) support that one of these channels, the O1 channel, facilitates water access to the Mn4CaO5 cluster during its S2→S3 and S3→S4→S0 state transitions, while a subsequent CryoEM study concluded that this channel is blocked in the cyanobacterium Synechocystis sp. PCC 6803, questioning the role of the O1 channel in water delivery. Employing site-directed mutagenesis we modified the two O1 channel bottleneck residues D1-E329 and CP43-V410 (T. vestitus numbering) and probed water access and substrate exchange via time resolved membrane inlet mass spectrometry. Our data demonstrates that water reaches the Mn4CaO5 cluster via the O1 channel in both wildtype and mutant PSII. In addition, the detailed analysis provides functional insight into the intricate protein-water-cofactor network near the Mn4CaO5 cluster that includes the pentameric, near planar 'water wheel' of the O1 channel.

通过单位点突变和膜入口质谱法探测光系统II O1通道的底物水通道。
光系统II通过提供电子和质子将二氧化碳还原为碳水化合物和我们呼吸的分子氧来维持地球上的生命。氧演化复合物的无机核心由地球上丰富的元素锰、钙和氧(Mn4CaO5簇)组成,并位于一个结合袋中,该结合袋通过充满水的通道连接到水周围,允许水的摄入和质子的出口。最近,利用从残留热聚球菌(T. vestitus)中分离的PSII进行的一系列晶体学和红外光谱研究支持了其中一个通道O1通道在Mn4CaO5的S2→S3和S3→S4→S0状态转变过程中促进水进入Mn4CaO5簇,而随后的CryoEM研究得出结论,该通道在蓝藻Synechocystis sp. PCC 6803中被阻断,质疑O1通道在水输送中的作用。我们采用定点诱变技术对两个O1通道瓶颈残基D1-E329和CP43-V410 (T. vestitus编号)进行了修饰,并通过时间分辨膜入口质谱法探测了水进入和底物交换。我们的数据表明,在野生型和突变型PSII中,水通过O1通道到达Mn4CaO5簇。此外,详细的分析提供了对Mn4CaO5簇附近复杂的蛋白质-水辅因子网络的功能洞察,包括五聚体,接近平面的O1通道的“水轮”。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Photosynthesis Research
Photosynthesis Research 生物-植物科学
CiteScore
6.90
自引率
8.10%
发文量
91
审稿时长
4.5 months
期刊介绍: Photosynthesis Research is an international journal open to papers of merit dealing with both basic and applied aspects of photosynthesis. It covers all aspects of photosynthesis research, including, but not limited to, light absorption and emission, excitation energy transfer, primary photochemistry, model systems, membrane components, protein complexes, electron transport, photophosphorylation, carbon assimilation, regulatory phenomena, molecular biology, environmental and ecological aspects, photorespiration, and bacterial and algal photosynthesis.
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