Yoshimura T, Matsushima A, Aki K
Biochim Biophys Acta. 1980 Sep 23;625(1):100-8. doi: 10.1016/0005-2795(80)90112-9.
The relationship between the structure and function of ferricytochrome c bound to the phosphoprotein phosvitin was investigated. The rates of reduction of phosvitin-bound ferricytochrome c by cytochrome b2, ascorbate and the superoxide radical generated by xanthine oxidase wer repressed where the binding ratio was less than half the maximum, but at higher ratios they were restored gradually with increase in the ratio. The affinity of cytochrome b2 for cytochrome c was not affected by binding of cytochrome c to phosvitin. The redox potential of the bond form was lower than that of the free form and only decreased with decrease in the ratio. The conformatin around the heme moiety and the electronic structure of the heme group of bound ferricytochrome c were similar to those of free ferricytochrome c, but the conformational stability in the vicinity of the prosthetic group was related to the binding ratio as ratios above half the maximum and was well correlated with the reduction rate. Since the binding of cytochrome c to phosvitin is much stronger at binding ratios below half the maximum, these results suggest that this binding strength exclusively affects the conformational flexibility of the heme crevice in the cytochrome molecule, thus altering the reduction rate.
研究了与磷蛋白卵黄高磷蛋白结合的高铁细胞色素c的结构与功能之间的关系。当结合比小于最大结合比的一半时，细胞色素b2、抗坏血酸和黄嘌呤氧化酶产生的超氧自由基对卵黄高磷蛋白结合的高铁细胞色素c的还原速率受到抑制，但在较高结合比时，它们随着结合比的增加而逐渐恢复。细胞色素b2对细胞色素c的亲和力不受细胞色素c与卵黄高磷蛋白结合的影响。结合形式的氧化还原电位低于游离形式，且仅随着结合比的降低而降低。结合的高铁细胞色素c的血红素部分周围的构象和血红素基团的电子结构与游离高铁细胞色素c的相似，但辅基附近的构象稳定性与结合比有关，结合比高于最大结合比的一半时，与还原速率密切相关。由于细胞色素c与卵黄高磷蛋白在结合比低于最大结合比的一半时结合更强，这些结果表明这种结合强度仅影响细胞色素分子中血红素裂隙的构象灵活性，从而改变还原速率。
