title: Crystal Structures Reveal that the Reaction Mechanism of Imidazoleglycerol-Phosphate Dehydratase Is Controlled by Switching Mn(II) Coordination.
abstract: Imidazoleglycerol-phosphate dehydratase (IGPD) catalyzes the Mn(II)-dependent dehydration of imidazoleglycerol phosphate (IGP) to 3-(1H-imidazol-4-yl)-2-oxopropyl dihydrogen phosphate during biosynthesis of histidine. As part of a program of herbicide design, we have determined a series of high-resolution crystal structures of an inactive mutant of IGPD2 from Arabidopsis thaliana in complex with IGP. The structures represent snapshots of the enzyme trapped at different stages of the catalytic cycle and show how substrate binding triggers a switch in the coordination state of an active site Mn(II) between six- and five-coordinate species. This switch is critical to prime the active site for catalysis, by facilitating the formation of a high-energy imidazolate intermediate. This work not only provides evidence for the molecular processes that dominate catalysis in IGPD, but also describes how the manipulation of metal coordination can be linked to discrete steps in catalysis, demonstrating one way that metalloenzymes exploit the unique properties of metal ions to diversify their chemistry.
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Claudine
authors.initials: C
authors.lastname: Bisson
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: K Linda
authors.initials: KL
authors.lastname: Britton
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Svetlana E
authors.initials: SE
authors.lastname: Sedelnikova
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: H Fiona
authors.initials: HF
authors.lastname: Rodgers
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Eadsforth
authors.affiliation: Syngenta, Jealott's Hill International Research Station, Bracknell RG42 6EY, UK.
authors.forename: Russell C
authors.initials: RC
authors.lastname: Viner
authors.affiliation: Syngenta, Jealott's Hill International Research Station, Bracknell RG42 6EY, UK.
authors.forename: Tim R
authors.initials: TR
authors.lastname: Hawkes
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK. Electronic address: p.baker@sheffield.ac.uk.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Baker
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute for Biomolecular Research, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK. Electronic address: d.rice@sheffield.ac.uk.
authors.forename: David W
authors.initials: DW
authors.lastname: Rice
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D056831:Coordination Complexes / Q000737:chemistry; D018360:Crystallography, X-Ray; D006540:Herbicides / Q000737:chemistry; D006836:Hydro-Lyases / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D056831:Coordination Complexes; D006540:Herbicides; D007093:Imidazoles; D010710:Phosphates; D008345:Manganese; D006836:Hydro-Lyases; C021434:imidazoleglycerolphosphate dehydratase