title: Radical SAM catalysis via an organometallic intermediate with an Fe-[5'-C]-deoxyadenosyl bond.
abstract: Radical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster to cleave SAM to initiate diverse radical reactions. These reactions are thought to involve the 5'-deoxyadenosyl radical intermediate, which has not yet been detected. We used rapid freeze-quenching to trap a catalytically competent intermediate in the reaction catalyzed by the radical SAM enzyme pyruvate formate-lyase activating enzyme. Characterization of the intermediate by electron paramagnetic resonance and (13)C, (57)Fe electron nuclear double-resonance spectroscopies reveals that it contains an organometallic center in which the 5' carbon of a SAM-derived deoxyadenosyl moiety forms a bond with the unique iron site of the [4Fe-4S] cluster. Discovery of this intermediate extends the list of enzymatic bioorganometallic centers to the radical SAM enzymes, the largest enzyme superfamily known, and reveals intriguing parallels to B12 radical enzymes.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Masaki
authors.initials: M
authors.lastname: Horitani
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Krista
authors.initials: K
authors.lastname: Shisler
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Broderick
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Rachel U
authors.initials: RU
authors.lastname: Hutcheson
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Kaitlin S
authors.initials: KS
authors.lastname: Duschene
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Marts
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA. bmh@northwestern.edu jbroderick@chemistry.montana.edu.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Hoffman
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. bmh@northwestern.edu jbroderick@chemistry.montana.edu.
authors.forename: Joan B
authors.initials: JB
authors.lastname: Broderick
mesh_terms: D000123:Acetyltransferases; D055162:Biocatalysis; D004578:Electron Spin Resonance Spectroscopy; D004798:Enzymes / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009942:Organometallic Compounds / Q000737:chemistry; D012436:S-Adenosylmethionine / Q000737:chemistry*; D014805:Vitamin B 12 / Q000737:chemistry
chemical_list: D004798:Enzymes; D007506:Iron-Sulfur Proteins; D009942:Organometallic Compounds; D012436:S-Adenosylmethionine; D000123:Acetyltransferases; C040285:pyruvate formate-lyase activating enzyme; D014805:Vitamin B 12