IDENTIFICATION OF MEMBRANE-BOUND C-TYPE CYTOCHROMES IN AN ACIDOPHILICFERROUS ION OXIDIZING BACTERIUM THIOBACILLUS-FERROOXIDANS

Three membrane-bound acid-stable cytochromes c with molecular masses o f 46, 30 and 21 kDa were characterized from a new Thiobacillus ferroox idans strain. They were solubilized with high concentrations of dodecy lmaltoside at pH 8. The 30 kDa cytochrome c was purified to a homogene ous state as established by SDS-PAGE analysis. It showed an absorption peak at 410 nm in the oxidized form and at 418, 523 and 552 nm in the reduced form. The 46 kDa cytochrome c co-purified with a non-heme pro tein of 36 kDa The amino acid composition and the N-terminal amino aci d sequence of the 46 kDa cytochrome c were determined and compared wit h those of the soluble 14 kDa and the membrane-bound 21, 22.3 and 68 k Da cytochromes c isolated from two different strains. The results clea rly show that this cytochrome is distinct from both the 22.3, 21 and 1 4 kDa cytochrome species, and exhibits some similarities with the 68 k Da cytochrome c as regards its amino acid composition.