High and low potential forms of the QA quinone electron acceptor in Photosystem II of Thermosynechococcus elongatus and spinach
High and low potential forms of the QA quinone electron acceptor in Photosystem II of Thermosynechococcus elongatus and spinach
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DOI：
10.1016/j.jphotobiol.2011.02.010
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发表时间：
2011-07-01
影响因子：
5.4
通讯作者：
Krieger-Liszkay, Anja
中科院分区：
文献类型：
--
作者：
Ido, Kunio;Gross, Christine M.;Krieger-Liszkay, Anja
用荧光滴定法测定了细长热聚球藻（Thermosynechococcuselongatus）光系统II（PSII）中Q（A）的氧化还原电位。在不存在Mn 4Ca（水氧化的活性位点）的情况下发现高电位形式（E-m = +60 +/-25 mV）。在常规滴定实验中难以测量的低电位形式（E-m = -60 +/-48 mV）可以通过交联活性酶来“锁定”。这表明Mn 4Ca的存在通过蛋白质中的显著结构变化被传递到醌位点。高电位和低电位形式的存在与我们实验室的植物、藻类和T。elongatus（Shibamoto等人，Biochemistry 48（2009）10682-10684）。在后一项工作中，与其他测量相比，Q（A）的电位向较低电位移动。在氧化还原介体的存在下滴定来自菠菜的Mn耗尽的PSII中的Q（A）的氧化还原电位，与没有介体的滴定相比，中点电位向更负的值移动80 mV。文献中（Q（A）/Q（A）（-））氧化还原对的中点电位的较低值可能是由于特定介体引起的扰动。(C)2011 Elsevier B. V.保留所有权利。
The redox potential of Q(A) in Photosystem II (PSII) from Thermosynechococcus elongatus was titrated monitoring chlorophyll fluorescence. A high potential form (E-m = +60 +/- 25 mV) was found in the absence of Mn4Ca, the active site for water oxidation. The low potential form (E-m = -60 +/- 48 mV), which is difficult to measure in conventional titration experiments, could be "locked in" by cross-linking the active enzyme. This indicates that the presence of Mn4Ca is relayed to the quinone site by significant structural changes in the protein. The presence of high and low potential forms agrees with what has been seen in plants, algae from our lab and in T. elongatus (Shibamoto et al., Biochemistry 48 (2009) 10682-10684). In the latter work, the potentials of Q(A) were shifted to lower potentials compared to other measurements. The redox potential of Q(A) in Mn-depleted PSII from spinach was titrated in the presence of redox mediators and the midpoint potential was shifted by 80 mV towards a more negative value compared to titrations without mediators. The lower values of the midpoint potential of the (Q(A)/Q(A)(-)) redox couple in the literature could be due to a perturbation due to a specific mediator. (C) 2011 Elsevier B.V. All rights reserved.