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首页> 外文期刊>Biochemistry >Side-chain interactions in the plastocyanin-cytochrome f complex.
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Side-chain interactions in the plastocyanin-cytochrome f complex.

机译：质体蓝蛋白-细胞色素f复合物中的侧链相互作用。

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摘要

Cytochrome f and plastocyanin are redox partners in the photosynthetic electron-transfer chain. Electron transfer from cytochrome f to plastocyanin occurs in a specific short-lived complex. To obtain detailed information about the binding interface in this transient complex, the effects of binding on the backbone and side-chain protons of plastocyanin have been analyzed by mapping NMR chemical-shift changes. Cytochrome f was added to plastocyanin up to 0.3 M equiv, and the plastocyanin proton chemical shifts were measured. Out of approximately 500 proton resonances, 86% could be observed with this method. Nineteen percent demonstrate significant chemical-shift changes and these protons are located in the hydrophobic patch (including the copper ligands) and the acidic patches of plastocyanin, demonstrating that both areas are part of the interface in the complex. This is consistent with the recently determined structure of the complex [Ubbink, M., Ejdeback, M., Karlsson, B. G., and Bendall, D. S. (1998) Structure 6, 323-335]. The largest chemical-shift changes are found around His87 in the hydrophobic patch, which indicates tight contacts and possibly water exclusion from this part of the protein interface. These results support the idea that electron transfer occurs via His87 to the copper in plastocyanin and suggest that the hydrophobic patch determines the specificity of the binding. The chemical-shift changes in the acidic patches are significant but small, suggesting that the acidic groups are involved in electrostatic interactions but remain solvent exposed. The existence of small differences between the present data and those used for the structure may imply that the redox state of the metals in both proteins slightly affects the structure of the complex. The chemical-shift mapping is performed on unlabeled proteins, making it an efficient way to analyze effects of mutations on the structure of the complex.
机译：细胞色素f和质体蓝蛋白是光合作用电子转移链中的氧化还原伙伴。电子从细胞色素f转移到质体蓝素中发生在特定的短寿命复合物中。为了获得有关此瞬态复合物中结合界面的详细信息，已通过绘制NMR化学位移变化分析了结合对质体蓝蛋白主链和侧链质子的影响。将细胞色素f添加至质体蓝蛋白中，直至0.3 M当量，然后测量质体蓝素质子化学位移。用这种方法，在大约500个质子共振中，可以观察到86％。 19％的化合物显示出显着的化学位移变化，并且这些质子位于疏水性斑块（包括铜配体）和质体蓝蛋白的酸性斑块中，表明这两个区域都是复合体界面的一部分。这与该复合物的最近确定的结构[Ubbink，M.，Ejdeback，M.，Karlsson，B.G。和Bendall，D.S。（1998）Structure 6，323-335]是一致的。在疏水区的His87附近发现最大的化学位移变化，这表明紧密接触，并可能从蛋白质界面的此部分排除水。这些结果支持这样的想法，即电子通过His87传递到质体蓝蛋白中的铜上，并表明疏水性补丁决定了结合的特异性。酸性补丁中的化学位移变化很大但很小，表明酸性基团参与静电相互作用，但仍暴露在溶剂中。当前数据与用于结构的数据之间存在小的差异可能意味着两种蛋白质中金属的氧化还原状态会稍微影响复合物的结构。化学位移映射是在未标记的蛋白质上进行的，从而使其成为分析突变对复合物结构影响的有效方法。

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