Mutagenesis of the proposed iron-sulfur cluster binding ligands in Escherichia coli biotin synthase

Biotin synthase (BioB) is a member of a family of enzymes that includes ana erobic ribonucleotide reductase and pyruvate formate lyase activating enzym e. These enzymes all use S-adenosylmethionine during turnover and contain t hree highly conserved cysteine residues that may act as ligands to an iron- sulfur cluster required for activity. Three mutant enzymes of BioB have bee n made, each with one cysteine residue (C53, 57, 60) mutated to alanine, Al l three mutant enzymes were inactive, hut they still exhibited the characte ristic UV-visible spectrum of a [2Fe-2S](2+) cluster similar to that of the wild-type enzyme. (C) 2000 Federation of European Biochemical Societies.