Characterization and expression of the co-transcribed cyc1 and cyc2 genes encoding the cytochrome c4 (c552) and a high-molecular-mass cytochrome c from Thiobacillus ferrooxidans ATCC33020

The sequence of the cyc1 gene encoding the Thiobacillus ferrooxidans ATCC 33020 c(552) cytochrome, shows that this cytochrome is a 21-kDa periplasmic ce-type cytochrome containing two similar monohaem domains. The kinetics of reduction and the fact that cytochromes C-4 are considered to be physiological electron donors of cytochrome oxidases suggest that the last steps of the iron respiratory chain are: rusticyanin --> cytochrome c(4) --> cytochrome oxidase. In Thiobacillus ferrooxidans, cyc1 is co-transcribed with the cyc2 gene, encoding a high-molecular-mass monohaem cytochrome c. This suggests that the cytochromes encoded by these genes belong to the same electron transfer chain. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.