Kinetic studies on 1:1 electron-transfer reactions involving blue copper proteins. Part 10. The assignment of binding sites in the reactions of plastocyanin (and azurin) with non-physiological protein redox partners
Kinetic studies on 1:1 electron-transfer reactions involving blue copper proteins. Part 10. The assignment of binding sites in the reactions of plastocyanin (and azurin) with non-physiological protein redox partners
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涉及蓝铜蛋白的 1:1 电子转移反应的动力学研究。
DOI：
10.1039/dt9840002775
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
A. Sykes
中科院分区：
文献类型：
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作者：
S. Chapman;C. Knox;A. Sykes
质体蓝素 PCu(II)（估计电荷 8–）、细胞色素 c(II)(8+) 和还原形式的高电位铁硫蛋白 Hipip(r)(3–) 的一当量还原已在 I= 0.10 M (NaCl) 下进行了研究。已经测试了三种效果。首先，注意到反应对 4.5-8.8 范围内 pH 值的不同反应。其次，观察到细胞色素 c(II)+ PCu(II) 反应与氧化还原惰性 [Pt(NH3)6]4+ 的竞争性抑制，但 Hipip(r)+ PCu(II) 没有。在第三种方法中，通过在残基 42-45 处连接 CrIII 进行修饰的 PCu(II) 与细胞色素 c(II) 的反应速度较慢，但与 Hipip(r) 的反应速度相同。所有三种方法均与细胞色素 c 在质体蓝蛋白上先前定义的 Tyr 83/42-45 位点上的反应一致。 Hipip(r) 的反应表明该还原剂在 PCu(II) 上的不同结合位点发生反应，该位点可能与 [Fe(CN)6]4– 使用的相同，即 His 87 位点。由于先前已证明质体蓝素在细胞色素 c 暴露的血红素边缘发生反应，因此可以得出结论，电子转移时 Cu 与 Fe 的分离约为 1。 20 A. 还考虑了 pH 对细胞色素 c(II) 和 Hipip(r) 还原天青蛋白、ACu(II)(1–) 的影响。
One-equivalent reductions of plastocyanin, PCu(II)(estimated charge 8–), with cytochrome c(II)(8+), and with high-potential iron–sulphur protein in the reduced form, Hipip(r)(3–), have been studied at I= 0.10 M (NaCl). Three effects have been tested for. First the different responses of the reactions to pH in the range 4.5–8.8 are noted. Secondly competitive inhibition of the reaction cytochrome c(II)+ PCu(II), but not Hipip(r)+ PCu(II), with redox-inactive [Pt(NH3)6]4+ has been observed. In the third approach PCu(II) modified by attachment of CrIII at residues 42–45 reacts more slowly with cytochrome c(II), but at the same rate with Hipip(r). All three approaches are consistent with cytochrome c reacting at the previously defined Tyr 83/42–45 site on plastocyanin. The responses with Hipip(r) suggest that this reductant reacts at a different binding site on PCu(II), which may be the same as that used by [Fe(CN)6]4–, namely the His 87 site. Since it has previously been demonstrated that plastocyanin reacts at the exposed haem edge of cytochrome c, it can be concluded that the Cu to Fe separation at the time of electron transfer is ca. 20 A. Effects of pH on the reduction of azurin, ACu(II)(1–), with cytochrome c(II) and Hipip(r) are also considered.