Hydrogen bonding between the Q(B) site ubisemiquinone and Ser-L223 in the bacterial reaction center: a combined spectroscopic and computational perspective.
Hydrogen bonding between the Q(B) site ubisemiquinone and Ser-L223 in the bacterial reaction center: a combined spectroscopic and computational perspective.
复制标题
细菌反应中心 Q(B) 位点泛半醌和 Ser-L223 之间的氢键：光谱和计算相结合的视角。
DOI：
10.1021/bi300834w
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发表时间：
2012
期刊：
影响因子：
2.9
通讯作者：
O'Malley,PatrickJ
中科院分区：
文献类型：
--
作者：
Martin,Erik;Baldansuren,Amgalanbaatar;Lin,Tzu-Jen;Samoilova,RimmaI;Wraight,ColinA;Dikanov,SergeiA;O'Malley,PatrickJ
在球形红细菌光合反应中心的QB位点，Ser-L223的羟基与第一次闪光后形成的泛半醌之间的氢键贡献是有争议的。在这项研究中，我们使用光谱和量子力学/分子力学（QM/MM）计算的组合，全面探讨这一主题。我们发现，ENDOR，ESEEM，和HYSCORE突变体L223 SA和野生型样品（WT）之间的光谱差异是可以忽略不计的，这表明只有轻微的扰动ubisemiquinone自旋密度的突变体样品。定性地，这表明在WT中Ser-L223羟基基团和半醌O 1原子之间不存在强氢键，因为在突变体中去除这种氢键应引起半醌中自旋密度的显著重新分布。我们定量地表明，使用QM/MM计算，其中Ser-L223羟基被旋转，以防止氢键形成与半醌的O 1原子的WT模型预测L223 SA突变体的变化可以忽略不计。这一点，连同更好的协议之间的关键QM/MM计算和实验超精细耦合的非氢键模型，使我们得出结论，没有强氢键之间形成的Ser-L223羟基和半醌O 1原子后，第一次闪光。这一发现的影响醌还原光合反应中心进行了讨论。
In the QBsite of theRhodobacter sphaeroidesphotosynthetic reaction center, the donation of a hydrogen bond from the hydroxyl group of Ser-L223 to the ubisemiquinone formed after the first flash is debatable. In this study, we use a combination of spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations to comprehensively explore this topic. We show that ENDOR, ESEEM, and HYSCORE spectroscopic differences between mutant L223SA and the wild-type sample (WT) are negligible, indicating only minor perturbations in the ubisemiquinone spin density for the mutant sample. Qualitatively, this suggests that a strong hydrogen bond does not exist in the WT between the Ser-L223 hydroxyl group and the semiquinone O1atom, as removal of this hydrogen bond in the mutant should cause a significant redistribution of spin density in the semiquinone. We show quantitatively, using QM/MM calculations, that a WT model in which the Ser-L223 hydroxyl group is rotated to prevent hydrogen bond formation with the O1atom of the semiquinone predicts negligible change for the L223SA mutant. This, together with the better agreement between key QM/MM calculated and experimental hyperfine couplings for the non-hydrogen-bonded model, leads us to conclude that no strong hydrogen bond is formed between the Ser-L223 hydroxyl group and the semiquinone O1atom after the first flash. The implications of this finding for quinone reduction in photosynthetic reaction centers are discussed.