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首页> 外文期刊>Biochemistry >Photocycle and vectorial proton transfer in a rhodopsin from the eukaryote oxyrrhis marina
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Photocycle and vectorial proton transfer in a rhodopsin from the eukaryote oxyrrhis marina

机译：真核生地中视紫红质中的光周期和矢量质子转移

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摘要

Retinylidene photoreceptors are ubiquitously present in marine protists as first documented by the identification of green proteorhodopsin (GPR). We present a detailed investigation of a rhodopsin from the protist Oxyrrhis marina (OR1) with respect to its spectroscopic properties and to its vectorial proton transport. Despite its homology to GPR, OR1's features differ markedly in its pH dependence. Protonation of the proton acceptor starts at pH below 4 and is sensitive to the ionic conditions. The mutation of a conserved histidine H62 did not influence the pKa value in a similar manner as in other proteorhodopsins where the charged histidine interacts with the proton acceptor forming the so-called His-Asp cluster. Mutational and pH-induced effects were further reflected in the temporal behavior upon light excitation ranging from femtoseconds to seconds. The primary photodynamics exhibits a high sensitivity to the environment of the proton acceptor D100 that are correlated to the different initial states. The mutation of the H62 does not affect photoisomerization at neutral pH. This is in agreement with NMR data indicating the absence of the His-Asp cluster. The subsequent steps in the photocycle revealed protonation reactions at the Schiff base coupled to proton pumping even at low pH. The main electrogenic steps are associated with the reprotonation of the Schiff base and internal proton donor. Hence, OR1 shows a different theme of the His-Asp organization where the low pKa of the proton acceptor is not dominated by this interaction, but by other electrostatic factors.
机译：最早在鉴定绿色蛋白视紫红质（GPR）的情况下，海洋生物家中普遍存在视黄素受体。我们目前就其光谱性质和其矢量质子运输方面对原生质的Oxyrrhis marina（OR1）视紫红质的详细研究。尽管与GPR具有同源性，但OR1的特征在其pH依赖性方面明显不同。质子受体的质子化从低于4的pH开始，并且对离子条件敏感。保守的组氨酸H62的突变不会以与其他蛋白视紫红质类似的方式影响pKa值，在其他蛋白视紫红质中，带电的组氨酸与质子受体相互作用形成所谓的His-Asp簇。突变和pH诱导的影响进一步反映在从飞秒到秒的光激发后的时间行为中。初级光动力学对与不同初始状态相关的质子受体D100的环境表现出很高的敏感性。 H62的突变不会影响中性pH下的光异构化。这与表明没有His-Asp簇的NMR数据一致。光循环中的后续步骤表明，即使在低pH值下，席夫碱的质子化反应也与质子泵激结合。主要的电学步骤与席夫碱和内部质子供体的质子化有关。因此，OR1显示了His-Asp组织的另一主题，在该主题中，质子受体的低pKa不受此相互作用的影响，而受其他静电因素的影响。

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