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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Exploring the proton pump and exit pathway for pumped protons in cytochrome ba_3 from Thermus thermophilus
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Exploring the proton pump and exit pathway for pumped protons in cytochrome ba_3 from Thermus thermophilus

机译：探索嗜热栖热菌细胞色素ba_3中质子泵和质子泵的出口通道

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摘要

The heme-copper oxygen reductases are redox-driven proton pumps. In the current work, the effects of mutations in a proposed exit pathway for pumped protons are examined in the ba_3-type oxygen reductase from Thermus thermophilus, leading from the propionates of heme a_3 to the interface between subunits Ⅰ and Ⅱ. Recent studies have proposed important roles for His376 and Asp372, both of which are hydrogen-bonded to propionate-A of heme a_3, and for Glu126~Ⅱ (subunit Ⅱ), which is hydrogen-bonded to His376. Based on the current results, His376, Glu126~Ⅱ, and Asp372 are not essential for either oxidase activity or proton pumping. In addition, Tyr133, which is hydrogen-bonded to propionate-D of heme a_3, was also shown not to be essential for function. However, two mutations of the residues hydrogen-bonded to propionate-A, Asp372lle and His376Asn, retain high electron transfer activity and normal spectral features but, in different preparations, either do not pump protons or exhibit substantially diminished proton pumping. It is concluded that either propionate-A of heme a_3 or possibly the cluster of groups centered about the conserved water molecule that hydrogen-bonds to both propionates-A and -D of heme a_3 is a good candidate to be the proton loading site.
机译：血红素铜氧还原酶是氧化还原驱动的质子泵。在当前的工作中，在嗜热栖热菌的ba_3型氧还原酶中，从血红素a_3的丙酸酯到亚基Ⅰ和Ⅱ之间的界面，研究了拟议的泵送质子出口途径中的突变效应。近年来的研究提出了两个重要的作用：His376和Asp372均与氢血红素a_3的丙酸酯-A键合； Glu126〜Ⅱ（Ⅱ亚基）与His376氢键合。根据目前的结果，His376，Glu126〜Ⅱ和Asp372对氧化酶活性或质子泵浦不是必需的。另外，还显示氢键合到血红素a_3的丙酸酯-D上的Tyr133对于功能不是必需的。但是，氢键合到丙酸酯-A的残基的两个突变Asp372lle和His376Asn保留了高电子转移活性和正常的光谱特征，但是在不同的制备方法中，要么不泵送质子，要么质子泵送显着减少。结论是，血红素a_3的丙酸酯-A或可能是围绕与氢键合的血红素a_3的丙酸酯-A和-D的保守水分子中心的基团簇是质子加载位点的良好候选者。

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