Application of Amber Suppression To Study the Role of Tyr M210 in Electron Transfer in Rhodobacter sphaeroides Photosynthetic Reaction Centers.

IF 2.8 2区 化学 Q3 CHEMISTRY, PHYSICAL
The Journal of Physical Chemistry B Pub Date : 2025-04-03 Epub Date: 2025-03-26 DOI:10.1021/acs.jpcb.5c00082
Khoi N Tran, Kaitlyn M Faries, Nikki Cecil Macasinag Magdaong, Irimpan I Mathews, Jared B Weaver, Jacob M Kirsh, Dewey Holten, Christine Kirmaier, Steven G Boxer
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引用次数: 0

Abstract

The initial light-induced electron transfer (ET) steps in the bacterial photosynthetic reaction center (RC) have been extensively studied and provide a paradigm for connecting structure and function. Although RCs have local pseudo-C2 symmetry, ET only occurs along the A branch of chromophores. Tyrosine M210 is a key symmetry-breaking residue adjacent to bacteriochlorophyll BA that bridges the primary electron donor P and the bacteriopheophytin acceptor HA. We used amber suppression to incorporate phenylalanine variants with different electron-withdrawing/-donating capabilities at the position M210. X-ray data generally reveal no appreciable structural changes due to the mutations. P* decay and P+HA- formation are multiexponential (∼2 to 9, ∼10 to 60, and ∼100 to 300 ps) and temperature dependent. The 1020 nm transient-absorption band of P+BA- is barely resolved for a few variants at 295 K and for none at 77 K. The results indicate a change from two-step ET for wild-type RCs to the dominance of one-step superexchange ET for the mutants. Resonance Stark spectroscopy reveals that the free energy of P+BA- changes by -57 to +66 meV among the phenylalanine variants. Because P+BA- apparently lies above P* in all phenylalanine variants, the perturbations primarily affect the energy denominator for superexchange mixing. The findings deepen insight into primary ET in the bacterial RC.

应用琥珀抑制研究Tyr M210在球形红杆菌光合反应中心电子转移中的作用。
细菌光合反应中心(RC)的初始光诱导电子转移(ET)步骤已被广泛研究,并为连接结构和功能提供了范例。虽然RCs具有局部伪c2对称性,但ET仅发生在发色团的A分支上。酪氨酸M210是细菌叶绿素BA附近的一个关键的对称性破坏残基,它连接了主要电子供体P和细菌叶绿素素受体HA。我们使用琥珀色抑制将具有不同吸电子/供电子能力的苯丙氨酸变体纳入M210位置。x射线数据通常显示没有明显的结构变化,由于突变。P*衰变和P+HA-形成是多指数(~ 2 ~ 9、~ 10 ~ 60和~ 100 ~ 300 ps)和温度相关的。P+BA-的1020nm瞬态吸收带在295k时几乎没有变化,而在77k时则没有变化。结果表明,从野生型RCs的两步ET到突变体的一步超交换ET的优势变化。共振斯塔克光谱结果表明,在苯丙氨酸变异体中,P+BA-的自由能变化幅度为-57 ~ +66 meV。由于在所有苯丙氨酸变体中P+BA-明显位于P*之上,因此扰动主要影响超交换混合的能量分母。这些发现加深了对细菌RC中原发性ET的了解。
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来源期刊
CiteScore
5.80
自引率
9.10%
发文量
965
审稿时长
1.6 months
期刊介绍: An essential criterion for acceptance of research articles in the journal is that they provide new physical insight. Please refer to the New Physical Insights virtual issue on what constitutes new physical insight. Manuscripts that are essentially reporting data or applications of data are, in general, not suitable for publication in JPC B.
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