Enzymatic cleavage of Clostridium pasteurianum apoferredoxin and reconstitution of the cleaved products.

Native ferredoxin from Clostridium pasteurianum proved to be resistant to proteolytic cleavage under anaerobic conditions, but was digested in the presence of air. Apoferredoxin was hydrolyzed by the proteinases used, while cobalt-substituted ferredoxin was resistant both under anaerobic and aerobic conditions. These studies indicate that metal binding of the protein stabilizes the folded state, which is extremely resistant to proteolytic attack. Sulfitolyzed apoferredoxin was subjected to specific cleavage by pepsin at pH 3.2, yielding two fragments. The fragments could be reconstituted to an unstable holoprotein with UV-visible absorption features like that of the native form.