Molar Extinction Coefficient and Iron and Sulfide Content of Clostridial Ferredoxin

Abstract

Abstract The molar extinction coefficient at 390 nm of Clostridium acidi-urici ferredoxin was determined by three independent methods: dry weight determination, amino acid analysis, and amino acid release by carboxypeptidase A treatment. The value of e390 based on the latter method is 30,600 m-1 cm-1. The content of iron was determined by atomic absorption spectrophotometry and the content of sulfide was determined from the amount of 35S-sulfide incorporated into ferredoxin in the reconstitution from apoferredoxin. Ferredoxin was found to contain 8 moles of both iron and sulfide.