Decolorization of malachite green by cytochrome c in the mitochondria of the fungus Cunninghamella elegans

Abstract We studied the decolorization of malachite green (MG) by the fungus Cunninghamella elegans . The mitochondrial activity for MG reduction was increased with a simultaneous increase of a 9-kDa protein, called CeCyt. The presence of cytochrome c in CeCyt protein was determined by optical absorbance spectroscopy with an extinction coefficient ( E 550–535 ) of 19.7 ± 6.3 mM −1  cm −1 and reduction potential of + 261 mV. When purified CeCyt was added into the mitochondria, the specific activity of CeCyt reached 440 ± 122 μmol min −1 mg −1 protein. The inhibition of MG reduction by stigmatellin, but not by antimycin A, indicated a possible linkage of CeCyt activity to the Qo site of the bc1 complex. The RT-PCR results showed tight regulation of the cecyt gene expression by reactive oxygen species. We suggest that CeCyt acts as a protein reductant for MG under oxidative stress in a stationary or secondary growth stage of this fungus.