期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：16
页码：7281-7283
DOI：10.1073/pnas.88.16.7281
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：As an electron transfer-driven proton pump, cytochrome c oxidase (ferrocytochrome-c:oxygen oxidoreductase, EC 1.9.3.1 ) must alternate between two conformations in each valence state of the redox element associated with ion translocation. Using second derivative absorption spectroscopy, the conformation of the cytochrome a cofactor has been investigated during steady-state turnover of this enzyme. Resting cytochrome c oxidase displays a transition for ferric cytochrome a at 430 nm. During aerobic steady-state turnover, this band is replaced by a ferrous cytochrome a transition at 450 nm. When anaerobicity is achieved, the transition occurs at 444 nm. The 450-nm-absorbing species is thus the dominant form during turnover, suggesting that conformational transitions of cytochrome a direct electron transfer during catalysis and may direct as well proton translocation in the last step of the respiratory electron transfer chain.
