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首页> 外文期刊>Biochemistry >Histidine 190-D1 and glutamate 189-D1 provide structural stabilization in photosystem II.
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Histidine 190-D1 and glutamate 189-D1 provide structural stabilization in photosystem II.

机译：组氨酸190-D1和谷氨酸189-D1在光系统II中提供结构稳定。

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摘要

In photosynthesis, photosystem II (PSII) conducts the light-driven oxidation of water to oxygen. Tyrosine Z is Tyr 161 of the D1 polypeptide; Z acts as an intermediary electron carrier in water oxidation. In this report, EPR spectroscopy was used to study the effect of His 190 and Glu 189 on Z* yield and reduction kinetics. Neither mutation has a significant impact on the EPR line shape of Z*. At room temperature and pH 7.5, the E189Q-D1 mutation has a single turnover Z* yield that is 84% compared to wild-type. The H190Q-D1 mutation decreases the Z* yield at room temperature by a factor of 2.6 but has a more modest effect (factor of 1.6) at -10 degrees C. The temperature dependence is shown to be primarily reversible. Neither mutation has a dramatic effect on Z* decay kinetics. The Z* minus Z FT-IR spectrum, recorded at pH 7.5 on H190Q, reveals perturbations, including an increased spectral contribution from a PSII chlorophyll. The Z* minus Z FT-IR spectrum, recorded at pH 7.5 on E189Q, shows perturbations, including a decreased contribution from the carboxylate side chain of a glutamate or aspartate. Temperature-dependent changes in H190Q-D1 and E189Q-D1 Z. yield are attributed to a reversible conformational change, which alters the electron-transfer rate from Z to P(680)(+). On the basis of these results, we conclude that H190 and E189 play a role in the structural stabilization of PSII. We postulate that some or all of the phenotypic changes observed in H190Q and E189Q mutants may be caused by structural alterations in PSII.
机译：在光合作用中，光系统II（PSII）将光驱动的水氧化成氧气。酪氨酸Z是D1多肽的Tyr 161; Z在水氧化中充当中间电子载体。在此报告中，使用EPR光谱研究了His 190和Glu 189对Z *收率和还原动力学的影响。两种突变都不会对Z *的EPR线形产生重大影响。在室温和pH值为7.5的情况下，与野生型相比，E189Q-D1突变的单次转化Z *产量为84％。 H190Q-D1突变在室温下将Z *产量降低2.6倍，但在-10摄氏度时具有更适度的作用（1.6倍）。显示出温度依赖性主要是可逆的。两种突变都不会对Z *衰变动力学产生显着影响。在H190Q的pH值为7.5时记录的Z *负Z FT-IR光谱显示出扰动，包括PSII叶绿素的光谱贡献增加。在E189Q的pH值为7.5时记录的Z *负Z FT-IR光谱显示出扰动，包括谷氨酸或天冬氨酸的羧酸根侧链贡献降低。 H190Q-D1和E189Q-D1 Z.产量的温度依赖性变化归因于可逆的构象变化，这改变了电子从Z到P（680）（+）的传输速率。根据这些结果，我们得出结论，H190和E189在PSII的结构稳定中起作用。我们假设在H190Q和E189Q突变体中观察到的某些或全部表型变化可能是PSII中的结构改变引起的。

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