Lambeth J D, Geren L M, Millett F
J Biol Chem. 1984 Aug 25;259(16):10025-9.
Modification of the three carboxyl groups on adrenodoxin using a water-soluble carbodiimide (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) caused a weakening of the binding of this iron-sulfur protein to both its electron donor protein, adrenodoxin reductase, and its electron acceptor protein, cytochrome P-450scc. Based upon the proximity of the modified groups, the site on adrenodoxin for interaction with the other two proteins is likely to be either identical or highly overlapping, and formation of a ternary complex among the proteins is precluded. Upon incubation of adrenodoxin and either adrenodoxin reductase or cytochrome P-450 plus the carbodiimide (1:1), covalently cross-linked species were formed. When all three proteins were incubated with the cross-linker, only the binary complexes were formed, and no higher order (e.g. 1:1:1 or 1:2:1) complexes were seen. These studies indicate that adrenodoxin forms exclusive binary complexes with its electron transfer partner proteins, and thus provide a physical explanation for the proposed role of adrenodoxin as a mobile electron shuttle between NADPH-adrenodoxin reductase and cytochrome P-450scc.
使用水溶性碳二亚胺（1-乙基-3-（3-二甲基氨基丙基）碳二亚胺）对肾上腺铁氧还蛋白上的三个羧基进行修饰，导致这种铁硫蛋白与其电子供体蛋白肾上腺铁氧还蛋白还原酶以及电子受体蛋白细胞色素P-450scc的结合减弱。基于修饰基团的位置，肾上腺铁氧还蛋白上与其他两种蛋白相互作用的位点可能相同或高度重叠，因此排除了蛋白之间形成三元复合物的可能性。将肾上腺铁氧还蛋白与肾上腺铁氧还蛋白还原酶或细胞色素P-450以及碳二亚胺（1:1）一起孵育时，会形成共价交联产物。当所有三种蛋白与交联剂一起孵育时，仅形成二元复合物，未观察到更高阶（例如1:1:1或1:2:1）的复合物。这些研究表明，肾上腺铁氧还蛋白与其电子传递伴侣蛋白形成排他性的二元复合物，从而为肾上腺铁氧还蛋白作为NADPH-肾上腺铁氧还蛋白还原酶和细胞色素P-450scc之间的移动电子穿梭体所提出的作用提供了物理解释。
