Two-dimensional HYSCORE spectroscopy reveals a histidine imidazole as the axial ligand to Chl3A in the M688HPsaA genetic variant of Photosystem I
Two-dimensional HYSCORE spectroscopy reveals a histidine imidazole as the axial ligand to Chl3A in the M688HPsaA genetic variant of Photosystem I
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二维 HYSCORE 光谱揭示了组氨酸咪唑作为 Photosystem I 的 M688HPsaA 遗传变体中 Chl3A 的轴向配体
DOI：
10.1016/j.bbabio.2021.148424
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Golbeck, John H.
中科院分区：
文献类型：
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作者：
Gorka, Michael;Gruszecki, Elijah;Charles, Philip;Kalendra, Vidmantas;Lakshmi, K.V.;Golbeck, John H.
最近的研究表明，光系统I（PS I）的六个核心叶绿素分子是高度耦合的，允许有效的创建和稳定的电荷分离状态。特别感兴趣的一个领域是主受体A0的身份和功能，因为影响其超快过程和氧化还原特性的因素尚未完全阐明。最近的研究表明，A0以Chl 2/Chl 3分子的二聚体形式存在，其中还原的A0自由基点−态具有有利于Chl 3的电子自旋密度的不对称分布。以前的实验工作中，这种配体被改变为一个硬碱（组氨酸，M688 HPsaA）显示严重影响的电子转移过程中，在A0和A1受体;分子动力学模拟进一步表明两个不同的构象PS I中的His残基的坐标和形成氢键的A0和A1辅因子，分别。在这项研究中，我们应用了二维HYSCORE光谱结合分子动力学模拟和密度泛函理论计算的M688 HPsaAvariant的研究。超精细参数的分析表明，组氨酸咪唑作为轴向配体的中心Mg 2+离子在Chl 3A在M688 HPsaA变体。虽然在配体身份的变化并不改变离域的Chl 2/Chl 3二聚体的电子密度，一个小的移位，离域的不对称性，再加上吸电子的配体的性质，最有可能占抑制前向电子转移的His连接的构象。
Recent studies on Photosystem I (PS I) have shown that the six core chlorophyllamolecules are highly coupled, allowing for efficient creation and stabilization of the charge-separated state. One area of particular interest is the identity and function of the primary acceptor, A0, as the factors that influence its ultrafast processes and redox properties are not yet fully elucidated. It was recently shown that A0exists as a dimer of the closely-spaced Chl2/Chl3molecules wherein the reduced A0radical dot−state has an asymmetric distribution of electron spin density that favors Chl3. Previous experimental work in which this ligand was changed to a hard base (histidine, M688HPsaA) revealed severely impacted electron transfer processes at both the A0and A1acceptors; molecular dynamics simulations further suggested two distinct conformations of PS I in which the His residue coordinates and forms a hydrogen bond to the A0and A1cofactors, respectively. In this study, we have applied 2D HYSCORE spectroscopy in conjunction with molecular dynamics simulations and density functional theory calculations to the study of the M688HPsaAvariant. Analysis of the hyperfine parameters demonstrates that the His imidazole serves as the axial ligand to the central Mg2+ion in Chl3Ain the M688HPsaAvariant. Although the change in ligand identity does not alter delocalization of electron density over the Chl2/Chl3dimer, a small shift in the asymmetry of delocalization, coupled with the electron withdrawing properties of the ligand, most likely accounts for the inhibition of forward electron transfer in the His-ligated conformation.