CHARACTERIZATION AND EXPRESSION OF THE CO-TRANSCRIBED CYC1 AND CYC2 GENES ENCODING THE CYTOCHROME C(4) (C(552)) AND A HIGH-MOLECULAR-MASS CYTOCHROME-C FROM THIOBACILLUS-FERROOXIDANS ATCC33020

The sequence of the cyc1 gene encoding the Thiobacillus ferrooxidans A TCC 33020 c(552) cytochrome, shows that this cytochrome is a 21-kDa pe riplasmic ce-type cytochrome containing two similar monohaem domains. The kinetics of reduction and the fact that cytochromes C-4 are consid ered to be physiological electron donors of cytochrome oxidases sugges t that the last steps of the iron respiratory chain are: rusticyanin - -> cytochrome c(4) --> cytochrome oxidase. In Thiobacillus ferrooxidan s, cyc1 is co-transcribed with the cyc2 gene, encoding a high-molecula r-mass monohaem cytochrome c. This suggests that the cytochromes encod ed by these genes belong to the same electron transfer chain. (C) 1998 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.