Mitochondrial Cytochrome b ₅₆₀

Abstract

Cytochrome b ₅₆₀ the succinate-ubiquinone (Q) reductase region of the mitochondrial electron transfer chain was first reported by Davis et al. (1,2). In spite of the detection of cytochrome b ₅₆₀ in various succinate -Q¹ reductase (3,4), and Complex II (5–7) preparations, this cytochrome has often been regarded as a contaminant of the denatured cytochromes from ubiquinol-cytochrome c reductase because it is not reducible by succinate, and the spectra of dithionite reduced cytochrome b ₅₆₀ in these preparations resembles the spectra of a mixture of denatured cytochromes b and c ₁ of ubiquinol-cytochrome c reductase. Thus, the importance of this particular cytochrome b ₅₆₀ has been slighted in the mammalian system. The participation of cytochrome b ₅₆₀ in succinate dehydrogenase (SDH) of Bacillus subtilis (8) and Neurospora crassa (9), however, is well recognized. Recently, a substrate reducible cytochrome ¿558 was detected in muscle mitochondrial succinate-Q reductase from Ascaris suum (10). In this paper we report the properties of mitochondrial cytochrome b560 and its possible function in succinate oxidation and fumarate reduction.