Role of the [2Fe-2S] Cluster in Recombinant Escherichia coli Biotin Synthase

Abstract

Biotin synthase (BioB) converts dethiobiotin into biotin by inserting a sulfur atom between C6 and C9 of dethiobiotin in an S-adenosylmethionine (SAM)-dependent reaction. The as-purified recombinant BioB from Escherichia coli is a homodimeric molecule containing one [2Fe-2S]2+ cluster per monomer. It is inactive in vitro without the addition of exogenous Fe. Anaerobic reconstitution of the as-purified [2Fe-2S]-containing BioB with Fe2+ and S2- produces a form of BioB that contains approximately one [2Fe-2S]2+ and one [4Fe-4S]2+ cluster per monomer ([2Fe-2S]/[4Fe-4S] BioB). In the absence of added Fe, the [2Fe-2S]/[4Fe-4S] BioB is active and can produce up to approximately 0.7 equiv of biotin..