Purification and characterization of cytochrome c3, ferredoxin, and rubredoxin isolated from Desulfovibrio desulfuricans Norway

Abstract

Different electron carriers of the non-desulfoviridin-containing, sulfate-reducing bacterium D. desulfuricans (strain Norway) were studied. Two nonheme Fe proteins, ferredoxin and rubredoxin, were purified. This ferredoxin contains 4 atoms of non-heme Fe and acid-labile S and 6 residues of cysteine/molecule. Its amino acid composition suggests that it is homologous with the other Desulfovibrio ferredoxins. The rubredoxin is also an acidic protein of 6000 MW and contains 1 atom of Fe and 4 cysteine residues/molecule. The amino acid composition and MW of the cytochrome c3 from D. desulfuricans (strain Norway 4) are reported. Its spectral properties are very similar to those of the other cytochromes c3 (MW, 13,000) of Desulfovibrio and show that it contains 4 hemes/molecule. This cytochrome has a very low redox potential and acts as a carrier in the coupling of hydrogenase and thiosulfate reductase in extracts of D. gigas and D. desulfuricans (strain Norway) in contrast to D. gigas cytochrome c3 (MW, 13,000). A comparison of the activities of the cytochrome c3 (MW, 13,000) of D. gigas and that of D. desulfuricans in this reaction suggests that these homologous proteins can have different specificity in the electron transfer chain of these bacteria.