当前位置: X-MOL 学术BBA Bioenerg. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
D1-S169A substitution of photosystem II reveals a novel S2-state structure.
Biochimica et Biophysica Acta (BBA) - Bioenergetics ( IF 3.4 ) Pub Date : 2020-08-27 , DOI: 10.1016/j.bbabio.2020.148301
Ipsita Ghosh 1 , Gourab Banerjee 1 , Krystle Reiss 1 , Christopher J Kim 2 , Richard J Debus 2 , Victor S Batista 1 , Gary W Brudvig 1
Affiliation  

In photosystem II (PSII), photosynthetic water oxidation occurs at the O2-evolving complex (OEC), a tetramanganese-calcium cluster that cycles through light-induced redox intermediates (S0–S4) to produce oxygen from two substrate water molecules. The OEC is surrounded by a hydrogen-bonded network of amino-acid residues that plays a crucial role in proton transfer and substrate water delivery. Previously, we found that D1-S169 was crucial for water oxidation and its mutation to alanine perturbed the hydrogen-bonding network. In this study, we demonstrate that the activation energy for the S2 to S1 transition of D1-S169A PSII is higher than wild-type PSII with a ~1.7–2.7× slower rate of charge recombination with QA relative to wild-type PSII. Arrhenius analysis of the decay kinetics shows an Ea of 5.87 ± 1.15 kcal mol−1 for decay back to the S1 state, compared to 0.80 ± 0.13 kcal mol−1 for the wild-type S2 state. In addition, we find that ammonia does not affect the S2-state EPR signal, indicating that ammonia does not bind to the Mn cluster in D1-S169A PSII. Finally, a QM/MM analysis indicates that an additional water molecule binds to the Mn4 ion in place of an oxo ligand O5 in the S2 state of D1-S169A PSII. The altered S2 state of D1-S169A PSII provides insight into the S2➔S3 state transition.



中文翻译:

光系统II的D1-S169A替代揭示了一种新颖的S2-状态结构。

在光系统II(PSII)中,光合水的氧化发生在O 2演化复合物(OEC)上,该复合物是四锰钙簇,通过光诱导的氧化还原中间体(S 0 –S 4)循环,从两个底物水分子中产生氧气。OEC周围是氨基酸残基的氢键网络,该网络在质子转移和底物水输送中起关键作用。以前,我们发现D1-S169对水氧化至关重要,并且其突变为丙氨酸会干扰氢键网络。在这项研究中,我们证明了S 2至S 1的活化能D1-S169A PSII的过渡大于与具有Q一〜1.7-2.7×较慢速率的电荷重组野生型PSII更高-相对于野生型PSII。衰变动力学的Arrhenius分析显示,衰减回S 1状态的E a为5.87±1.15 kcal mol -1,而野生型S 2状态的E a为0.80±0.13 kcal mol -1。此外,我们发现氨气不会影响S 2状态EPR信号,表明氨气不会与D1-S169A PSII中的Mn团簇结合。最后,QM / MM分析表明,另外一个水分子与Mn4离子结合,代替了S 2中的氧代配体O5。D1-S169A PSII的状态。改变的小号2 D1-S169A PSII的状态提供了洞察在S 2 ➔S 3状态转变。

更新日期:2020-09-07
down
wechat
bug