Abstract
SUMMARY: Low-temperature difference spectra of gradient-purified mitochondria from Sterigmatomyces halophilus revealed the presence of a-, b- and c-type cytochromes, spectrally similar to those of other yeasts. Fourth-order finite difference analysis resolved the broad α-band of b- and c-type cytochromes into eight peaks. Absorption maxima at about 539, 543·5 and 547·5 nm were attributed to one, or perhaps two, cytochrome(s) c that are loosely bound to the mitochondrial membrane. Cytochrome c1 was identified at 550·5 to 551·5 nm. Maxima at about 554, 556, 559 and 562 nm were attributed to three or four distinct b-type cytochromes on the basis of their differential reduction by NADH, dithionite, or ascorbate plus N, N,-N', N',-tetramethyl-p-phenylenediamine in the absence or presence of antimycin. Difference spectra in the presence of CO or cyanide indicated the presence of cytochromes a (600 nm) and a3 (608 nm). Finite difference analysis of the cytochromes c oxidase peak centred at 600 nm revealed two components; the major component at 600 nm was identified as cytochrome a and the minor component at 605 nm as cytochrome a3. A further CO-binding haemoprotein was tentatively identified as cytochrome o.