Electron transfer reagent binding sites on plastocyanin
Electron transfer reagent binding sites on plastocyanin
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质体蓝蛋白上的电子转移试剂结合位点
作者：
D. Cookson;M. Hayes;P. Wright
电子转移是所有生物系统中的一个重要过程。小无机配合物和各种金属蛋白之间的电子转移反应动力学已得到广泛研究1-5。最近对质体蓝素（光合电子传递链的重要组成部分）的电子传递反应的研究表明，6-9 无机氧化还原试剂，如六氰基铁（III）离子（Fe（CN）63−6）和三（1,10-菲咯啉）钴（III）离子（Co(1,10-phen)33+）在电子传递步骤之前与蛋白质形成离散的复合物。在这里，我们使用高分辨率核磁共振波谱 (NMR) 研究了菜豆 (Phaseolus vulgaris) 和黄瓜 (Cucumis sativm) 中的质体蓝素与这些氧化还原试剂的铬 (III) 类似物 K3Cr(CN)6 和 Cr(1,10-phen)3 (ClO4)3 的相互作用。这些复合物与质体蓝素的结合具有高度特异性，我们确定了两个相距约 15 Å 的结合位点，这显然主要是由静电相互作用决定的。指出了进出铜原子的两种不同的电子转移途径。
Electron transfer is an essential process in all biological systems. The kinetics of electron transfer reactions between small inorganic complexes and a variety of metalloproteins have been extensively studied1–5. Recent studies on the electron transfer reactions of plastocyanin, an essential component of the photosynthetic electron transport chain, have shown6–9 that inorganic redox reagents such as the hexacyanoferrate(III) ion (Fe(CN)63−6) and the tris(1,10-phenanthroline)cobalt(III) ion (Co(1,10-phen)33+) form discrete complexes with the protein before the electron transfer step. Here, we have used high resolution nuclear magnetic resonance spectroscopy (NMR) to study the interaction of plastocyanins from French bean (Phaseolus vulgaris) and cucumber (Cucumis sativm) with the chromium(III) analogues of these redox reagents, K3Cr(CN)6 and Cr(1,10-phen)3 (ClO4)3. The binding of these complexes to plastocyanin is highly specific and we identify two binding sites, separated by about 15 Å, which are apparently determined primarily by electrostatic interactions. Two distinct electron transfer pathways to and from the copper atom are indicated.