Purification and characterization of ferredoxin from Peptostreptococcus productus (strain Marburg)

Ferredoxin was purified to apparent homogeneity from cell extracts of the homoacetogen Peptostreptococcus productus (strain Marburg). The yield was 70 g ferredoxin per g wet cells of P. productus. The UV-vis spectrum exhibited characteristics of a typical clostridial ferredoxin spectrum with a molar extinction coefficient ₃₈₅ of 30000 M^-1 cm^-1 and an A₃₈₅/A₂₈₀ ratio of 0.76. The molecular weight M_r was near 5700 as calculated from the amino acid composition. The protein contained per mol 9.9 mol iron, 8.2 mol acid-labile sulfide, and near 7 mol cysteine indicating the presence of two 4 Fe/4 S clusters. The redox potential was determined to be-410 mV. The purified ferredoxin was reduced with carbon monoxide by the carbon monoxide dehydrogenase from crude extracts and by the partially enriched enzyme of P. productus.