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首页> 外文期刊>Biochemistry >Glutamate 286 in cytochrome aa3 from Rhodobacter sphaeroides is involved in proton uptake during the reaction of the fully-reduced enzyme with dioxygen
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Glutamate 286 in cytochrome aa3 from Rhodobacter sphaeroides is involved in proton uptake during the reaction of the fully-reduced enzyme with dioxygen

机译：谷氨酸286来自乳菌斯氏菌的细胞色素AA3在全氧化酶与二恶英的反应期间参与质子摄取

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摘要

The reaction with dioxygen of solubilized fully-reduced wild-type and EQ(I-286) (exchange of glutamate 286 of subunit I for glutamine) mutant cytochrome c oxidase from Rhodobacter sphaeroides has been studied using the flow-flash technique in combination with optical absorption spectroscopy. Proton uptake was measured using a pH-indicator dye. In addition, internal electron-transfer reactions were studied in the absence of oxygen. Glutamate 286 is found in a proton pathway proposed to be used for pumped protons from the crystal structure of cytochrome c oxidase from Paracoccus denitrificans [Iwata et al. (1995) Nature 376, 660-669; E278 in P.d. numbering]. It is the residue closest to the oxygen-binding binuclear center that is clearly a part of the pathway. The results show that the wild-type enzyme becomes fully oxidized in a few milliseconds at pH 7.4 and displays a biphasic proton uptake from the medium. In the EQ(I-286) mutant enzyme, electron transfer after formation of the peroxy intermediate is impaired, CuA remains reduced, and no protons are taken up from the medium. Thus, the results suggest that E(I-286) is necessary for proton uptake after formation of the peroxy intermediate and transfer of the fourth electron to the binuclear center. The results also indicate that the proton uptake associated with formation of the ferryl intermediate controls the electron transfer from CuA to heme a.
机译：使用流动闪光技术与光学闪光技术研究了与溶解的全型野生型和EQ（I-286）的二氧化溶液（I-286）的二氧化碳（I-286）（谷氨酰胺I的谷氨酸谷氨酸I.谷氨酸）交换的反应（谷氨酰胺I）的突变体细胞色素C氧化酶进行研究。吸收光谱。使用pH指示剂染料测量质子吸收。此外，在没有氧气的情况下研究了内部电子转移反应。谷氨酸286中的质子途径发现，该质子途径中提出用于从伴随裂藻菌的细胞色素C氧化酶的晶体结构泵浦质子[iwata等人。 （1995）自然376,660-669; E278在P.D.编号]。它是最接近氧结合的双核中心的残留物，显然是途径的一部分。结果表明，野生型酶在pH 7.4的几毫秒内完全氧化，并显示从培养基的双相质子摄取。在EQ（I-286）突变体酶中，在形成过氧中间体后的电子转移受到损害，CUA保持降低，并且从培养基中没有取出质子。因此，结果表明E（I-286）是在形成过氧中间体和第四电子至双核中心的过氧中间体和转移后的质子吸收所必需的。结果还表明，与渡轮中间体的形成相关的质子吸收控制了Cua至血红素A的电子转移。

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