Yin Ying, Tso Shih-Chia, Yu Chang-An, Yu Linda
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
Biochim Biophys Acta. 2009 Jul;1787(7):913-9. doi: 10.1016/j.bbabio.2009.03.018. Epub 2009 Apr 5.
Previous studies indicate that the three-subunit cytochrome bc(1) core complex of Rhodobacter sphaeroides contains a fraction of the electron transfer activity of the wild-type enzyme. Addition of subunit IV to the core complex increases electron transfer activity to the same level as that of the wild-type complex. This activity increase may result from subunit IV preventing electron leakage, from the low potential electron transfer chain, and reaction with molecular oxygen, producing superoxide anion. This suggestion is based on the following observations: (1) the extent of cytochrome b reduction in the three-subunit core complex, by ubiquinol, in the presence of antimycin A, never reaches the same level as that in the wild-type complex; (2) the core complex produces 4 times as much superoxide anion as does the wild-type complex; and (3) when the core complex is reconstituted with subunit IVs having varying reconstitutive activities, the activity increase in reconstituted complexes correlates with superoxide production decrease and extent of cytochrome b reduction increase.
先前的研究表明，球形红杆菌的三亚基细胞色素bc(1)核心复合物具有野生型酶的一部分电子转移活性。向核心复合物中添加亚基IV可将电子转移活性提高到与野生型复合物相同的水平。这种活性增加可能是由于亚基IV阻止了电子从低电位电子传递链泄漏以及与分子氧反应产生超氧阴离子。这一推测基于以下观察结果：(1)在存在抗霉素A的情况下，泛醇使三亚基核心复合物中的细胞色素b还原程度从未达到野生型复合物中的水平；(2)核心复合物产生的超氧阴离子是野生型复合物的4倍；(3)当用具有不同重组活性的亚基IV重构核心复合物时，重构复合物中的活性增加与超氧产生减少以及细胞色素b还原程度增加相关。
