The oxidation of exogenous cytochrome c by mitochondria

FEBS Letters

Casey, Robert¹  Wikström, Mårten¹ 

[1] Department of Medical Chemistry, University of Helsinki, Siltavuorenpenger 10 A, SF-00170 Helsinki, Finland

关键词: Mitochondrial outer membrane;    Cytochrome oxidase;    Proton pumping;    NADH-cytochrome b5reductase;    FCCP;    carbonyl cyanide p-trifluoromethoxyphenylhydrazone;    TMPD;    N;    N;    N ';    N '-tetramethyl-p-phenylenediamine;   

DOI  :  10.1016/0014-5793(85)80796-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Several reports in the past have dealt with the oxidation of cytochrome c added to suspensions of rat liver mitochondria. Yet, it is generally believed that the cytochrome cannot penetrate the outer membrane. Probably it has been assumed that the permeability of the outer membrane to cytochrome c is very low but finite, and that fast oxidation may be observed if time is allowed for sufficient penetration before initiation of electron flow. Here we show that this view is false. The main fraction of rat liver mitochondria, as isolated by conventional procedures, does not catalyse any significant oxidation of added cytochrome c, even after prolonged incubation. The observed appreciable oxidation of added cytochrome c is catalysed by a very small fraction (5–12%) of the mitochondria that apparently has a damaged outer membrane. Consequently, the turnover of cytochrome oxidase is very high in this fraction during oxidation of added cytochrome c. This finding readily explains why Moyle and Mitchell (e.g., FEBS Lett. 88 (1978) 268-272; 90 (1978) 361-365) have failed to observe proton translocation by cytochrome oxidase during oxidation of ferrocytochrome c added to rat liver mitochondria, which has been their main reason for rejecting the proton-pumping function of cytochrome oxidase.

【 授权许可】

Unknown