Influence of Polar Mutations on the Electronic and Structural Properties of QA-· in Bacterial Reaction Centers.
Influence of Polar Mutations on the Electronic and Structural Properties of QA-· in Bacterial Reaction Centers.
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极性突变对细菌反应中心 QA-· 电子和结构特性的影响。
DOI：
10.1021/acs.jpcb.2c04371
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Dikanov,SergeiA
中科院分区：
文献类型：
--
作者：
Taguchi,AlexanderT;Wraight,ColinA;Dikanov,SergeiA
Reaction centers fromRhodobacter sphaeroideswith residue M265 mutated from isoleucine to threonine, serine, and asparagine (M265IT, M265IS, and M265IN, respectively) in theQA–·state are studied by high-resolution electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance spectroscopy methods to investigate the structural characteristics of these mutants influencing the redox properties of theQAsite. All three mutants decrease the redox midpoint potential (Em) ofQAby ∼0.1 V, yet the mechanism for this drop inEmis unclear. In this work, we examine (i) the hydrogen bonding interactions betweenQA–·and residues histidine M219 and alanine M260, (ii) the electron spin density distribution of the semiquinone, and (iii) the orientations of the ubiquinone methoxy substituents.13C measurements show no significant contribution of methoxy dihedral angles to the observed decrease inEmfor theQAmutants. Instead,14N three-pulse ESEEM data suggest that electrostatic or hydrogen bond formation between the mutated M265 side chain and His-M219Nδmay be involved in the observed lowering of theQAmidpoint potential. For mutant M265IN, analysis of the proton hyperfine couplings reveals a weakened hydrogen bond network, resulting in an alteredQA–·spin density distribution. The magnetic resonance study presented here is most consistent with an electrostatic or structural perturbation of the His-M219Nδhydrogen bond in these mutants as a mechanism for the ∼0.1 V decrease inQAEm.
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影响因子：
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