Publications by authors named "Dominique Florentin"
Biotin synthase, a member of the "radical SAM" family, catalyzes the final step of the biotin biosynthetic pathway, namely, the insertion of a sulfur atom into dethiobiotin (DTB). The active form of the enzyme contains two iron-sulfur clusters, a [4Fe-4S](2+) cluster liganded by Cys-53, Cys-57, and Cys-60 and the S-adenosylmethionine (AdoMet or SAM) cosubstrate and a [2Fe-2S](2+) cluster liganded by Cys-97, Cys-128, Cys-188, and Arg-260. Single-point mutation of each of these six conserved cysteines produced inactive variants.
View Article and Find Full Text PDFBiotin synthase, a member of the "radical SAM" family, catalyzes the final step of the biotin biosynthetic pathway, namely, the insertion of a sulfur atom into dethiobiotin. The as-isolated enzyme contains a [2Fe-2S](2+) cluster, but the active enzyme requires an additional [4Fe-4S](2+) cluster, which is formed in the presence of Fe(NH(4))(2)(SO(4))(2) and Na(2)S in the in vitro assay. The role of the [4Fe-4S](2+) cluster is to mediate the electron transfer to SAM, while the [2Fe-2S](2+) cluster is involved in the sulfur insertion step.
View Article and Find Full Text PDFBiotin synthase, a member of the "radical-SAM" family, produces biotin by inserting a sulfur atom between C-6 and C-9 of dethiobiotin. Each of the two saturated carbon atoms is activated through homolytic cleavage of a C-H bond by a deoxyadenosyl radical, issued from the monoelectronic reduction of S-adenosylmethionine (SAM or AdoMet). An important unexplained observation is that the enzyme produces only 1 mol of biotin per enzyme monomer.
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- Biotin synthase contains (2Fe-2S)(2+) clusters under aerobic conditions, which can be converted to (4Fe-4S)(2+,+) through reduction processes.
- In experiments using Mössbauer spectroscopy, a mixture of (2Fe-2S)(2+) and (4Fe-4S)(2+) clusters was observed in the presence of specific iron and sulfur sources, but the cluster composition remained unchanged with a physiological reducing system.
- The introduction of dethiobiotin led to degradation of (2Fe-2S)(2+) while leaving (4Fe-4S)(2+) intact, suggesting that the reduced (4Fe-4S) cluster plays a role in AdoMet cleavage
Article Synopsis
- Biotin synthase only contains [2Fe-2S](2+) clusters when isolated under aerobic conditions.
- Previous studies indicated that under reducing and anaerobic conditions, biotin synthase could be reconstituted with various iron-sulfur clusters including [4Fe-4S](2+) and [2Fe-2S](2+).
- Using (57)Fe Mössbauer spectroscopy, it was found that aerobically grown cells contain a mix of [4Fe-4S](2+) and [2Fe-2S](2+) clusters, supporting the idea that both cluster types may play important roles in the enzyme's function.