Reductive cleavage of S-adenosylmethionine by biotin synthase from Escherichia coli

Ollagnier-de Choudens, Sandrine, Sanakis, Yiannis, Hewitson, Kirsty S., Roach, Peter, Münck, Eckard and Fontecave, Marc (2002) Reductive cleavage of S-adenosylmethionine by biotin synthase from Escherichia coli. The Journal of Biological Chemistry, 277 (16), 13449-13454. (doi:10.1074/jbc.M111324200).

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 Mössbauer 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.

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Contributors

Author: Peter Roach

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