Reducibility of cytochromeb in mitochondrial inner membrane |
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Authors: | Takayuki Ozawa A. N. Malviya Yohei Takahashi Kunio Yagi |
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Affiliation: | (1) Institute of Biochemistry, University of Nagoya, Nagoya, Japan;(2) Present address: Department of Pathology, Faculty of Medicine, University of Nagoya, Nagoya, Japan;(3) Department of Biochemistry, S.N. Medical College, Agra, India |
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Abstract: | When mitochondrial inner membrane was disintegrated into Complex I-III, IV, and oligomycin-sensitive ATPase, about 50% of cytochromeb in Complex I-III was readily reduced with NADH, as judged by the appearance of a peak at 562 nm, while in whole mitochondria less than 25% of cytochromeb was reduced by succinate. On addition of antimycin to the substrate-reduced Complex I-III, cytochromeb was further reduced to 71% of the total, and the peak at 562 nm was red-shifted to 564 nm as in the case of dithionite reduction. These results indicate that the 562 nm and 564 nm peaks, at 29°C correspond, respectively, tob560 andb562.5 at 77°K of Davis et al. [7] and to bK and bT of Chance et al. [2]. When Complex I-III and oligomycin-sensitive ATPase were reconstituted to form a membrane, about 60% of cytochromeb in Complex I-III was readily reduced with NADH. In this case the 562 nm peak was not red-shifted. However, the difference spectrum of NADH-reduced membraneminus that in the presence of deoxycholate showed a peak at 565 nm. A mirror image of the difference spectrum was obtained on addition of an uncoupler,m-chlorocarbonyl cyanide phenylhydrazone. This is characteristic for bT. These results support the idea that the occurrence of spectral peaks of bT and bK is not due to two species but to single speciesAbbreviations OS-ATPase oligomycin sensitive ATPase - CCCP m-chlorocarbonyl cyanide phenylhydrazone - F1 coupling factor one - OSCP oligomycinsensitivity-conferring protein |
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