Abstract
Mitochondrial cysteine desulfurase is an essential component of the machinery for iron-sulfur cluster biosynthesis. It has been known that human cysteine desulfurase that is catalytically active in vitro can be prepared by overexpressing in Escherichia coli cells two protein components of this system, the cysteine desulfurase protein NFS1 and the auxiliary protein ISD11. We report here that this active preparation contains, in addition, the holo-form of E. coli acyl carrier protein (Acp). We have determined the stoichiometry of the complex to be [Acp](2):[ISD11](2):[NFS1](2). Acyl carrier protein recently has been found to be an essential component of the iron-sulfur protein biosynthesis machinery in mitochondria; thus, because of the activity of [Acp](2):[ISD11](2):[NFS1](2) in supporting iron-sulfur cluster assembly in vitro, it appears that E. coli Acp can substitute for its human homologue.