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Gunhild Layer, Eric Kervio, Gaby Morlock, Dirk W. Heinz, Dieter Jahn, Janos Retey, Wolf-Dieter Schubert

Structural and functional comparison of HemN to other radical SAM enzymes

Keywords: BioB, [4Fe-4S] cluster, HemN, littorine mutase, MoaA, radical SAM enzymes, S-adenosyl-l-methionine

Radical SAM enzymes have only recently been recognized as an ancient family sharing an unusual radical-based reaction mechanism. This late appreciation is due to the extreme oxygen sensitivity of most radical SAM enzymes, making their characterization particularly arduous. Nevertheless, realization that the novel apposition of the established cofactors S-adenosylmethionine and [4Fe-4S] cluster creates an explosive source of catalytic radicals, the appreciation of the sheer size of this previously neglected family, and the rapid succession of three successfully solved crystal structures within a year have ensured that this family has belatedly been noted. In this review, we report the characterization of two enzymes: the established radical SAM enzyme, HemN or oxygen-independent coproporphyrinogen III oxidase from Escherichia coli, and littorine mutase, a presumed radical SAM enzyme, responsible for the conversion of littorine to hyoscyamine in plants. The enzymes are compared to other radical SAM enzymes and in particular the three reported crystal structures from this family, HemN, biotin synthase and MoaA, are discussed.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 386, 10/2005
Pages: 971 - 980

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