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 (Norway strain) have been studied. Two nonheme iron proteins, ferredoxin and rubredoxin, have been purified. This ferredoxin contains four atoms of non heme iron and acid labile sulfur and six residues of cysteine per molecule. Its amino acid composition suggests that it is homologous with the other Desulfovibrio ferredoxins. The rubredoxin is also an acidic protein of 6,000 molecular weight and contains one atom of iron and four cysteine residues per molecule. The amino acid composition and molecular weight 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 (molecular weight, 13,000) of Desulfovibrio and show that it contains four hemes per molecule. This cytochrome has a very low redox potential and acts as carrier in the coupling of hydrogenase and thiosulfate reductase in extracts of D. gigas and D. desulfuricans (Norway strain) in contrast to D. gigas cytochrome c3 (molecular weight, 13,000). A comparison of the activities of the cytochrome c3 (molecular weight, 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.