Zhou J S, Nocek J M, DeVan M L, Hoffman B M
Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
Science. 1995 Jul 14;269(5221):204-7. doi: 10.1126/science.7618081.
Copper-substituted cytochrome c (CuCc) has been used as a structurally faithful, redoxinert inhibitor to probe the mechanism of electron transfer (ET) between Cc molecules and cytochrome c peroxidase (CcP). This inhibitor enhances photoinduced ET quenching of the triplet excited state of a zinc-substituted protein (ZnCcP or ZnCc) by its iron(III) partner (Fe3+Cc or Fe3+CcP). These results show that CcP and Cc form a ternary complex in which one Cc molecule binds tightly at a surface domain of CcP having low ET reactivity, whereas the second Cc molecule binds weakly to the 1:1 complex at a second domain with markedly greater (approximately 10(3)) reactivity. These results also rule out the possibility that Cc bound at the second domain cooperatively enhances ET to Cc at the first domain. The multiphasic kinetics observed for the photoproduced ET intermediate do not reflect electron self-exchange between two Cc molecules within the ternary complex.
铜取代细胞色素c（CuCc）已被用作一种结构忠实、氧化还原惰性的抑制剂，以探究细胞色素c（Cc）分子与细胞色素c过氧化物酶（CcP）之间的电子转移（ET）机制。这种抑制剂通过其铁（III）伙伴（Fe3+Cc或Fe3+CcP）增强了锌取代蛋白（ZnCcP或ZnCc）三重激发态的光诱导ET猝灭。这些结果表明，CcP和Cc形成了一个三元复合物，其中一个Cc分子紧密结合在CcP具有低ET反应性的表面结构域，而第二个Cc分子则在具有明显更高（约10³）反应性的第二个结构域与1:1复合物弱结合。这些结果也排除了在第二个结构域结合的Cc协同增强向第一个结构域的Cc进行ET的可能性。光产生的ET中间体观察到的多相动力学并不反映三元复合物内两个Cc分子之间的电子自交换。
