Auxiliary Iron–Sulfur Cofactors in Radical SAM Enzymes☆
Biochimica et Biophysica Acta 1853 (2015) 1316–1334 Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbamcr Review Auxiliary iron–sulfur cofactors in radical SAM enzymes☆ Nicholas D. Lanz a, Squire J. Booker a,b,⁎ a Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, United States b Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, United States article info abstract Article history: A vast number of enzymes are now known to belong to a superfamily known as radical SAM, which all contain a Received 19 September 2014 [4Fe–4S] cluster ligated by three cysteine residues. The remaining, unligated, iron ion of the cluster binds in Received in revised form 15 December 2014 contact with the α-amino and α-carboxylate groups of S-adenosyl-L-methionine (SAM). This binding mode Accepted 6 January 2015 facilitates inner-sphere electron transfer from the reduced form of the cluster into the sulfur atom of SAM, Available online 15 January 2015 resulting in a reductive cleavage of SAM to methionine and a 5′-deoxyadenosyl radical. The 5′-deoxyadenosyl Keywords: radical then abstracts a target substrate hydrogen atom, initiating a wide variety of radical-based transforma- – Radical SAM tions. A subset of radical SAM enzymes contains one or more additional iron sulfur clusters that are required Iron–sulfur cluster for the reactions they catalyze. However, outside of a subset of sulfur insertion reactions, very little is known S-adenosylmethionine about the roles of these additional clusters. This review will highlight the most recent advances in the identifica- Cofactor maturation tion and characterization of radical SAM enzymes that harbor auxiliary iron–sulfur clusters.
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