title: Spectroscopic approaches to elucidating novel iron-sulfur chemistry in the "radical-Sam" protein superfamily.
abstract: Electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and Mössbauer spectroscopies and other physical methods have provided important new insights into the radical-SAM superfamily of proteins, which use iron-sulfur clusters and S-adenosylmethionine to initiate H atom abstraction reactions. This remarkable chemistry involves the generation of the extremely reactive 5'-deoxyadenosyl radical, the same radical intermediate utilized in B12-dependent reactions. Although early speculation focused on the possibility of an organometallic intermediate in radical-SAM reactions, current evidence points to novel chemistry involving a site-differentiated [4Fe-4S] cluster. The focus of this forum article is on one member of the radical-SAM superfamily, pyruvate formate-lyase activating enzyme, and how physical methods, primarily EPR and ENDOR spectroscopies, are contributing to our understanding of its structure and mechanism. New ENDOR data supporting coordination of the methionine moiety of SAM to the unique site of the [4Fe-4S]2+/+ cluster are presented.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Walsby
authors.forename: Danilo
authors.initials: D
authors.lastname: Ortillo
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Mbako R
authors.initials: MR
authors.lastname: Nnyepi
authors.forename: William E
authors.initials: WE
authors.lastname: Broderick
authors.forename: Brian M
authors.initials: BM
authors.lastname: Hoffman
authors.forename: Joan B
authors.initials: JB
authors.lastname: Broderick
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D003839:Deoxyadenosines / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004789:Enzyme Activation; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism*; D005609:Free Radicals / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D009942:Organometallic Compounds / Q000737:chemistry*; D015204:Spectroscopy, Mossbauer / Q000379:methods
chemical_list: D003839:Deoxyadenosines; D004798:Enzymes; D005609:Free Radicals; D007506:Iron-Sulfur Proteins; D009942:Organometallic Compounds; C033714:5'-deoxyadenosine