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首页> 外文期刊>Biochemistry >A PH-DEPENDENT POLARITY CHANGE AT THE BINUCLEAR CENTER OF REDUCED CYTOCHROME C OXIDASE DETECTED BY FTIR DIFFERENCE SPECTROSCOPY OF THE CO ADDUCT
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A PH-DEPENDENT POLARITY CHANGE AT THE BINUCLEAR CENTER OF REDUCED CYTOCHROME C OXIDASE DETECTED BY FTIR DIFFERENCE SPECTROSCOPY OF THE CO ADDUCT

机译：用Co FTIR光谱检测还原的细胞色素C氧化酶双核中心的PH依赖极性变化

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摘要

A pH-dependent polarity change at the heme-copper binuclear center of the aa(3)-type cytochrome c oxidase from Rhodobacter sphaeroides has been identified by low-temperature FTIR difference spectroscopy. ''Light''-minus-''dark'' FTIR difference spectra of the fully reduced CO-enzyme adduct were recorded at a range of pH, and the dominance of different populations of bound CO, alpha and beta, was found to vary with pH. An apparent pK(a) of about 7.3 for the transition was obtained. The alpha and beta forms are differentiated by different polarities at the heme-copper binuclear center of the enzyme, sensed by the stretching frequencies of CO bound either to the heme a(3) Fe or to Cu-B. Several site-directed mutants in the vicinity of the heme-copper center are shown to favor either the alpha or the beta forms of the enyzme, suggesting that what is being monitored is an equilibrium between two conformations of the reduced form of the oxidase. Recent resonance Raman evidence has been presented demonstrating that the alpha and beta forms of the R. sphaeroides oxidase exist at room temperature; therefore, the pH-dependent change in the polarity in the vicinity of the heme-copper center may be functionally significant.
机译：已通过低温FTIR差异光谱法鉴定了球形球形红球菌aa（3）型细胞色素c氧化酶的血红素-铜双核中心的pH依赖性极性变化。在一定的pH值范围内记录了完全还原的CO-酶加合物的“亮”-负-“暗” FTIR差异光谱，发现结合的CO，α和β的不同种群的优势不同与pH值。对于该转变，获得了约7.3的表观pK（a）。 α和β形式的区别在于酶在血红素-铜双核中心的极性不同，由结合到血红素a（3）Fe或Cu-B的CO的拉伸频率感测到。在血红素-铜中心附近的几个定点突变体显示偏爱酶的α或β形式，表明所监测的是氧化酶还原形式的两个构象之间的平衡。最近的共振拉曼证据已经提出，表明球形红球菌氧化酶的α和β形式在室温下存在。因此，血红铜中心附近极性的pH依赖性变化可能在功能上很重要。

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