title: Organometallic Complex Formed by an Unconventional Radical S-Adenosylmethionine Enzyme.
abstract: Pyrococcus horikoshii Dph2 (PhDph2) is an unusual radical S-adenosylmethionine (SAM) enzyme involved in the first step of diphthamide biosynthesis. It catalyzes the reaction by cleaving SAM to generate a 3-amino-3-carboxypropyl (ACP) radical. To probe the reaction mechanism, we synthesized a SAM analogue (SAMCA), in which the ACP group of SAM is replaced with a 3-carboxyallyl group. SAMCA is cleaved by PhDph2, yielding a paramagnetic (S = 1/2) species, which is assigned to a complex formed between the reaction product, α-sulfinyl-3-butenoic acid, and the [4Fe-4S] cluster. Electron-nuclear double resonance (ENDOR) measurements with (13)C and (2)H isotopically labeled SAMCA support a π-complex between the C═C double bond of α-sulfinyl-3-butenoic acid and the unique iron of the [4Fe-4S] cluster. This is the first example of a radical SAM-related [4Fe-4S](+) cluster forming an organometallic complex with an alkene, shedding additional light on the mechanism of PhDph2 and expanding our current notions for the reactivity of [4Fe-4S] clusters in radical SAM enzymes.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Min
authors.initials: M
authors.lastname: Dong
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Masaki
authors.initials: M
authors.lastname: Horitani
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Boris
authors.initials: B
authors.lastname: Dzikovski
authors.affiliation: Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02453, United States.
authors.forename: Maria-Eirini
authors.initials: ME
authors.lastname: Pandelia
authors.affiliation: Department of Chemistry and Department of Biochemistry and Molecular Biology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Carsten
authors.initials: C
authors.lastname: Krebs
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Jack H
authors.initials: JH
authors.lastname: Freed
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Hoffman
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.|Howard Hughes Medical Institute, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Hening
authors.initials: H
authors.lastname: Lin
mesh_terms: D000475:Alkenes / Q000737:chemistry; D016880:Anisotropy; D002087:Butyrates / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D004798:Enzymes / Q000737:chemistry*; D006639:Histidine / Q000031:analogs & derivatives / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D043902:Pyrococcus horikoshii / Q000201:enzymology*; D012436:S-Adenosylmethionine / Q000737:chemistry*
chemical_list: D000475:Alkenes; D002087:Butyrates; D004798:Enzymes; D007506:Iron-Sulfur Proteins; D009942:Organometallic Compounds; D006639:Histidine; C479121:3-butenoic acid; D002244:Carbon; C027527:diphthamide; D012436:S-Adenosylmethionine; D007501:Iron