Properties of a Paracoccus denitrificans mutant deleted in cytochrome c550 indicate that a copper protein can substitute for this cytochrome in electron transport to nitrite, nitric oxide and nitrous oxide

摘要

Summary: Disruption of the gene for the periplasmic cytochrome c550 in Paracoccus denitrificans did not result in substantial alteration of rates of electron flow from physiological substrates to the reductases for nitrite, nitric oxide and nitrous oxide, thus confirming and extending earlier findings. In wild-type cells the chelating agent diethyldithiocarbamate (DDC) caused a partial inhibition of these electron transport processes. When the same concentrations of this inhibitor were added to a mutant of P. denitrificans in which the gene for cytochrome c550 was specifically disrupted an almost complete inhibition of these reactions was observed. It is known from previous work with the closely related organism Thiosphaera pantotropha that DDC effectively and rapidly removes copper from the periplasmic pseudoazurin that is also found in P. denitrificans. Therefore, it is concluded that in the absence of cytochrome c550, a copper protein, probably pseudoazurin, acts as the electron carrier between the cytochrome bc1 complex and the reductases for nitrite, nitric oxide and nitrous oxide. Cells with the gene for cytochrome c550 deleted continued to give a positive Nadi test.