1995 Volume 18 Issue 8 Pages 1045-1048
The reconstitution of the iron-sulfur cluster of spinach ferredoxin was examined in vitro using low and high molecular bound sulfur components as sulfur donors. Bound sulfur was rapidly converted to acid-labile sulfur to form an iron-sulfur center in the presence of dihydrolipoate and iron. Reconstitution yields of above 95% were obtained with cystine trisulfide (CT, 0.25mM) and sulfur-bound albumin (SBA, 1.0mM) at 37°C, pH 7.3, following 60min incubation. Spectroscopic features and biological activity of the reconstituted ferredoxin were identical to those of the native holo-protein. The acid-labile sulfur content found in the isolated reconstituted ferredoxin was 2atoms/mol protein, similar to the theoretical value. A possible role for bound sulfur in mammalian cells is indicated and discussed.