Oxidation-reduction potentials of cytochromes in Ascaris muscle mitochondria: high-redox-potential cytochrome b558 in complex II (succinate-ubiquinone reductase)
Takamiya, S.; Kita, K.; Matsuura, K.; Furushima, R.; Oya, H.
Biochemistry International 21(6): 1073-1080
1990
ISSN/ISBN: 0158-5231 PMID: 2080921 Document Number: 348588
Oxidation-reduction midpoint potentials (Ems) were determined at pH 7.0 for cytochromes in the anaerobic respiratory chain of Ascaris mitochondria by redox titration techniques. Cytochrome b558, which is associated with complex II that functions as fumarate reductase in the terminal step of the respiratory chain, was shown to have an Em of -34 mV in the isolated complex II and -54 mV in mitochondria. These values are much higher than the value reported for mammalian cytochrome b560 of complex II, showing a unique feature of Ascaris cytochrome b558. In contrast, Ems of cytochromes c + c1 and cytochrome b559.5 were determined in situ to be 235 mV and 78 mV, respectively, which are comparable to those of their mammalian counterparts.