title: Structural basis for the erythro-stereospecificity of the L-arginine oxygenase VioC in viomycin biosynthesis.
abstract: The nonheme iron oxygenase VioC from Streptomyces vinaceus catalyzes Fe(II)-dependent and alpha-ketoglutarate-dependent Cbeta-hydroxylation of L-arginine during the biosynthesis of the tuberactinomycin antibiotic viomycin. Crystal structures of VioC were determined in complexes with the cofactor Fe(II), the substrate L-arginine, the product (2S,3S)-hydroxyarginine and the coproduct succinate at 1.1-1.3 A resolution. The overall structure reveals a beta-helix core fold with two additional helical subdomains that are common to nonheme iron oxygenases of the clavaminic acid synthase-like superfamily. In contrast to other clavaminic acid synthase-like oxygenases, which catalyze the formation of threo diastereomers, VioC produces the erythro diastereomer of Cbeta-hydroxylated L-arginine. This unexpected stereospecificity is caused by conformational control of the bound substrate, which enforces a gauche(-) conformer for chi(1) instead of the trans conformers observed for the asparagine oxygenase AsnO and other members of the clavaminic acid synthase-like superfamily. Additionally, the substrate specificity of VioC was investigated. The side chain of the L-arginine substrate projects outwards from the active site by undergoing interactions mainly with the C-terminal helical subdomain. Accordingly, VioC exerts broadened substrate specificity by accepting the analogs L-homoarginine and L-canavanine for Cbeta-hydroxylation.
authors.affiliation: Department of Chemistry, Philipps-University Marburg, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Helmetag
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Samel
authors.forename: Michael G
authors.initials: MG
authors.lastname: Thomas
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Marahiel
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Essen
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019159:Nonheme Iron Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010105:Oxygenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism; D013302:Streptomyces / Q000201:enzymology*; D013379:Substrate Specificity; D014756:Viomycin / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D019159:Nonheme Iron Proteins; D001120:Arginine; D010105:Oxygenases; C497198:vioC protein, Chromobacterium violaceum; D014756:Viomycin