The D1-V185N mutation alters substrate water exchange by stabilizing alternative structures of the Mn4Ca-cluster in photosystem II
The D1-V185N mutation alters substrate water exchange by stabilizing alternative structures of the Mn4Ca-cluster in photosystem II
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DOI：
10.1016/j.bbabio.2020.148319
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发表时间：
2021-01-01
影响因子：
4.3
通讯作者：
Messinger, Johannes
中科院分区：
文献类型：
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作者：
de Lichtenberg, Casper;Avramov, Anton P.;Messinger, Johannes
在光合作用中，色素-蛋白质复合物光系统II（PSII）的放氧复合物（OEC）协调水的氧化。先前报道，将V185 N突变引入D1蛋白质中会大大减缓O-2释放，并强烈扰乱Mn 4Ca簇周围的水网络。采用时间分辨膜入口质谱法，我们在这里测量的（H2O）-O-18/（H2O）-O-16-交换动力学的快（W-f）和慢（W-s）交换底物沃茨结合在S-1，S-2和S-3状态的PSII核心复合物的Mn 4Ca簇分离自野生型和D1 -V185 N菌株集胞藻PCC 6803。我们发现，在S-1和S-2状态下，W-s的交换率增加，而在S-3状态下，W-f和W-s的交换率都降低。此外，我们使用EPR光谱来表征Mn 4Ca簇及其与氧化还原活性D1-Tyr 161（Y-Z）的相互作用。在S-2状态下，我们观察到V185 N-PSII中的多线信号大大减弱，可以通过添加氨来恢复。在Si状态下的分裂信号不受影响，而在S-3状态下的分裂信号在D1-V185 N突变体中不存在。这些发现是合理的建议，N185残基稳定的Mn 4Ca簇的Mn 1位点通过氢键的额外的水衍生的配体的结合。基板水结合的网站的影响进行了讨论。
In photosynthesis, the oxygen-evolving complex (OEC) of the pigment-protein complex photosystem II (PSII) orchestrates the oxidation of water. Introduction of the V185N mutation into the D1 protein was previously reported to drastically slow O-2-release and strongly perturb the water network surrounding the Mn4Ca cluster. Employing time-resolved membrane inlet mass spectrometry, we measured here the (H2O)-O-18/(H2O)-O-16-exchange kinetics of the fast (W-f) and slow (W-s) exchanging substrate waters bound in the S-1, S-2 and S-3 states to the Mn4Ca cluster of PSII core complexes isolated from wild type and D1 -V185N strains of Synechocystis sp. PCC 6803. We found that the rate of exchange for W-s was increased in the S-1 and S-2 states, while both W-f and W-s exchange rates were decreased in the S-3 state. Additionally, we used EPR spectroscopy to characterize the Mn4Ca cluster and its interaction with the redox active D1-Tyr161 (Y-Z). In the S-2 state, we observed a greatly diminished multiline signal in the V185N-PSII that could be recovered by addition of ammonia. The split signal in the Si state was not affected, while the split signal in the S-3 state was absent in the D1-V185N mutant. These findings are rationalized by the proposal that the N185 residue stabilizes the binding of an additional water-derived ligand at the Mn1 site of the Mn4Ca cluster via hydrogen bonding. Implications for the sites of substrate water binding are discussed.