Journal
BIOCHEMISTRY
Volume 40, Issue 28, Pages 8352-8358Publisher
AMER CHEMICAL SOC
DOI: 10.1021/bi010463x
Keywords
-
Categories
Funding
- NIGMS NIH HHS [R01 GM059175, GM-59175] Funding Source: Medline
Ask authors/readers for more resources
Biotin synthase catalyzes the insertion of a sulfur atom between the saturated C6 and C9 carbons of dethiobiotin. Catalysis requires AdoMet and flavodoxin and generates 5 ' -deoxyadenosine and methionine, suggesting that biotin synthase is an AdoMet-dependent radical enzyme. Biotin synthase (BioB) is aerobically purified as a dimer of 38.4 kDa monomers that contains I - 1.5 [2Fe-2S](2+) clusters per monomer and can be reconstituted with exogenous iron, sulfide, and reductants to contain up to two [4Fe-4S] clusters per monomer. The iron-sulfur clusters may play a dual role in biotin synthase: a reduced iron-sulfur cluster is probably involved in radical generation by mediating the reductive cleavage of AdoMet, while recent in vitro labeling studies suggest that an iron-sulfur cluster also serves as the immediate source of sulfur for the biotin thioether ring. Consistent with this dual role for iron-sulfur clusters in biotin synthase, we have found that the protein is stable, containing one [2Fe-2S](2+) cluster and one [4Fe-4S](2+) cluster per monomer. In the present study, we demonstrate that this mixed cluster state is essential for optimal activity. We follow changes in the Fe and S content and UV/visible and EPR spectra of the enzyme during a single turnover and conclude that during catalysis the [4Fe-4S](2+) cluster is preserved while the [2Fe-2S](2+) cluster is destroyed. We propose a mechanism fur incorporation of sulfur into dethiobiotin in which a sulfur atom is oxidatively extracted from the [2Fe-2S](2+) cluster.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available