The exchange of the fast substrate water in the S(2) state of photosystem II is limited by diffusion of bulk water through channels - implications for the water oxidation mechanism.
The exchange of the fast substrate water in the S(2) state of photosystem II is limited by diffusion of bulk water through channels - implications for the water oxidation mechanism.
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在光系统II的S（2）状态下，快速基质水的交换受到大量水通过通道扩散的限制-这意味着水氧化机制。
DOI：
10.1039/d1sc02265b
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发表时间：
2021-10-06
期刊：
影响因子：
8.4
通讯作者：
Messinger J
中科院分区：
文献类型：
--
作者：
de Lichtenberg C;Kim CJ;Chernev P;Debus RJ;Messinger J
我们呼吸的分子氧是由与光系统II（PSII）中的Mn 4CaO 5簇结合的水衍生氧物种产生的。目前的研究指出，中心氧桥O 5作为“慢交换基质水（Ws）”，而在S2状态下，末端水配体W2和W3都被讨论为“快交换基质水（Wf）”。分配的Wf的一个关键点是它是否与散装水的交换是有限的障碍，导致Mn 4CaO 5集群的通道。在这项研究中，我们测量了H216 O/H218 O基板水交换率在S2和S3状态的PSII核心复合物从野生型（WT）集胞藻属PCC 6803，并从两个突变体，D1-D 61 A和D1-E189 Q，预计将改变水的访问通过Cl 1/O 4通道和O 1通道，分别。我们发现Wf和Ws的交换速率不受E189 Q突变（O 1通道）的影响，但受到D 61 A突变（Cl 1/O 4通道）的强烈干扰。它的结论是，所有的通道限制了内水池附近的Mn 4CaO 5集群的同位素平衡，并D 61参与了这样一个障碍。在D 61 A突变体中，该屏障降低，使得Wf交换更迅速地发生。这一发现消除了主要的论点对钙结合W3作为快速基板水在S2状态，即无差别的Wf交换率对Ca/Sr的替代。进入光合作用中的放氧复合物受到连接Mn 4CaO 5催化剂与本体水的通道中的特定屏障的限制。连同其他最近的数据，这一发现允许分配两个衬底沃茨。
The molecular oxygen we breathe is produced from water-derived oxygen species bound to the Mn4CaO5 cluster in photosystem II (PSII). Present research points to the central oxo-bridge O5 as the ‘slow exchanging substrate water (Ws)’, while, in the S2 state, the terminal water ligands W2 and W3 are both discussed as the ‘fast exchanging substrate water (Wf)’. A critical point for the assignment of Wf is whether or not its exchange with bulk water is limited by barriers in the channels leading to the Mn4CaO5 cluster. In this study, we measured the rates of H216O/H218O substrate water exchange in the S2 and S3 states of PSII core complexes from wild-type (WT) Synechocystis sp. PCC 6803, and from two mutants, D1-D61A and D1-E189Q, that are expected to alter water access via the Cl1/O4 channels and the O1 channel, respectively. We found that the exchange rates of Wf and Ws were unaffected by the E189Q mutation (O1 channel), but strongly perturbed by the D61A mutation (Cl1/O4 channel). It is concluded that all channels have restrictions limiting the isotopic equilibration of the inner water pool near the Mn4CaO5 cluster, and that D61 participates in one such barrier. In the D61A mutant this barrier is lowered so that Wf exchange occurs more rapidly. This finding removes the main argument against Ca-bound W3 as fast substrate water in the S2 state, namely the indifference of the rate of Wf exchange towards Ca/Sr substitution. Access to the oxygen-evolving complex in photosynthesis is restricted by specific barriers in the channels connecting the Mn4CaO5 catalyst with bulk water. Together with other recent data, this finding allows assigning the two substrate waters.
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影响因子：
4.3
作者：
Boussac, Alain;Rutherford, A. William;Sugiura, Miwa
通讯作者：
Sugiura, Miwa
影响因子：
4.3
作者：
Arató, A;Bondarava, N;Krieger-Liszkay, A
通讯作者：
Krieger-Liszkay, A
DOI：
10.1073/pnas.1915879117
发表时间：
2020-01-07
影响因子：
11.1
作者：
Cheah, Mun Hon;Zhang, Miao;Messinger, Johannes
通讯作者：
Messinger, Johannes
影响因子：
2.9
作者：
Askerka, Mikhail;Wang, Jimin;Batista, Victor S.
通讯作者：
Batista, Victor S.
影响因子：
4.3
作者：
Boussac, Alain;Ugur, Ilke;Rutherford, A. William
通讯作者：
Rutherford, A. William