title: Demonstration That the Radical S-Adenosylmethionine (SAM) Enzyme PqqE Catalyzes de Novo Carbon-Carbon Cross-linking within a Peptide Substrate PqqA in the Presence of the Peptide Chaperone PqqD.
abstract: The radical S-adenosylmethionine (SAM) protein PqqE is predicted to function in the pyrroloquinoline quinone (PQQ) biosynthetic pathway via catalysis of carbon-carbon bond formation between a glutamate and tyrosine side chain within the small peptide substrate PqqA. We report here that PqqE activity is dependent on the accessory protein PqqD, which was recently shown to bind PqqA tightly. In addition, PqqE activity in vitro requires the presence of a flavodoxin- and flavodoxin reductase-based reduction system, with other reductants leading to an uncoupled cleavage of the co-substrate SAM. These results indicate that PqqE, in conjunction with PqqD, carries out the first step in PQQ biosynthesis: a radical-mediated formation of a new carbon-carbon bond between two amino acid side chains on PqqA.
authors.affiliation: From the Department of Chemistry, Department of Molecular and Cell Biology, and California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720.
authors.forename: Ian
authors.identifier: http://orcid.org/0000-0003-1805-1415
authors.initials: I
authors.lastname: Barr
authors.affiliation: From the Department of Chemistry, California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720.
authors.forename: John A
authors.initials: JA
authors.lastname: Latham
authors.affiliation: From the Department of Chemistry, California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Iavarone
authors.affiliation: From the Department of Chemistry.
authors.forename: Teera
authors.initials: T
authors.lastname: Chantarojsiri
authors.affiliation: Department of Molecular and Cell Biology, and.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Hwang
authors.affiliation: From the Department of Chemistry, Department of Molecular and Cell Biology, and California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720 klinman@berkeley.edu.
authors.forename: Judith P
authors.initials: JP
authors.lastname: Klinman
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009161:Mycobacterium / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C095466:PqqA protein, Methylobacterium extorquens; C091163:PqqD protein, Methylobacterium extorquens; D010450:Endopeptidases; C098959:PqqE protein, Methylobacterium extorquens
keywords: PQQ; S-adenosylmethionine (SAM); SPASM domain; flavoprotein; iron-sulfur protein; peptides; post-translational modification (PTM); radical SAM