title: Structural basis for activation of class Ib ribonucleotide reductase.
abstract: The class Ib ribonucleotide reductase of Escherichia coli can initiate reduction of nucleotides to deoxynucleotides with either a Mn(III)2-tyrosyl radical (Y•) or a Fe(III)2-Y• cofactor in the NrdF subunit. Whereas Fe(III)2-Y• can self-assemble from Fe(II)2-NrdF and O2, activation of Mn(II)2-NrdF requires a reduced flavoprotein, NrdI, proposed to form the oxidant for cofactor assembly by reduction of O2. The crystal structures reported here of E. coli Mn(II)2-NrdF and Fe(II)2-NrdF reveal different coordination environments, suggesting distinct initial binding sites for the oxidants during cofactor activation. In the structures of Mn(II)2-NrdF in complex with reduced and oxidized NrdI, a continuous channel connects the NrdI flavin cofactor to the NrdF Mn(II)2 active site. Crystallographic detection of a putative peroxide in this channel supports the proposed mechanism of Mn(III)2-Y• cofactor assembly.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Amie K
authors.initials: AK
authors.lastname: Boal
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Cotruvo
authors.forename: JoAnne
authors.initials: J
authors.lastname: Stubbe
authors.forename: Amy C
authors.initials: AC
authors.lastname: Rosenzweig
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D003067:Coenzymes / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D005296:Ferrous Compounds / Q000737:chemistry / Q000378:metabolism; D005486:Flavin Mononucleotide / Q000737:chemistry / Q000378:metabolism; D005418:Flavodoxin / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010545:Peroxides / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D003067:Coenzymes; D029968:Escherichia coli Proteins; D005296:Ferrous Compounds; D005418:Flavodoxin; D008024:Ligands; D016877:Oxidants; D010545:Peroxides; D021122:Protein Subunits; D008345:Manganese; D005486:Flavin Mononucleotide; C532352:NrdF protein, E coli; D012264:Ribonucleotide Reductases; D010100:Oxygen