Reductive cleavage of S-adenosylmethionine by biotin synthase from Escherichia coli.
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Ollagnier-de Choudens S, Sanakis Y, Hewitson KS, Roach P, Munck E, Fontecave M
Reductive cleavage of S-adenosylmethionine by biotin synthase from Escherichia coli.
J Biol Chem. 2002 Apr 19;277(16):13449-54. Epub 2002 Feb 7.
- PubMed ID
- 11834738 [ View in PubMed]
- Abstract
Biotin synthase (BioB) catalyzes the insertion of a sulfur atom between the C6 and C9 carbons of dethiobiotin. Reconstituted BioB from Escherichia coli contains a [4Fe-4S](2+/1+) cluster thought to be involved in the reduction and cleavage of S-adenosylmethionine (AdoMet), generating methionine and the reactive 5'-deoxyadenosyl radical responsible for dethiobiotin H-abstraction. Using EPR and Mossbauer spectroscopy as well as methionine quantitation we demonstrate that the reduced S = 1/2 [4Fe-4S](1+) cluster is indeed capable of injecting one electron into AdoMet, generating one equivalent of both methionine and S = 0 [4Fe-4S](2+) cluster. Dethiobiotin is not required for the reaction. Using site-directed mutagenesis we show also that, among the eight cysteines of BioB, only three (Cys-53, Cys-57, Cys-60) are essential for AdoMet reductive cleavage, suggesting that these cysteines are involved in chelation of the [4Fe-4S](2+/1+) cluster.