The Function of B Cytochrome in Complex II (Succinate-Ubiquinone Oxidoreductase)

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Complex II (succinate-ubiquinone oxidoreductase) is an important enzyme complex of both the TCA cycle and of the aerobic respiratory chain of mitochondria in eukaryotic cell and prokaryotic organisms. In this study, we have characterized the cytochrome b in complex II as described below.1) To dissociate the subunits of complex II, ionic detergent "sarkosyl" was most useful.2) In vivo reconstitution system of complex II from sdh genes separated in multiple plasmids in the Escherichia coli Cell has been established.3) cDNA library of Ascarismuscle has been constructed and positive clones for cytochorme b subunit of compleX II have been screened immunologically.4) Amino acid sequence of iron-sulfur subunit in human liver was deduced from cDNA which was isolated by immunoscreening.5) Oxidation-reduction potentials of cytochromes in muscle mitochondria of Ascaris and purified complex II were determined and compared with those in mammalian mitochondria. Oxidation-reduction potential of cytochrome b_<558> of Ascaris complex II was higher than that of bovine heart complex II.