title: Atomic details of near-transition state conformers for enzyme phosphoryl transfer revealed by MgF-3 rather than by phosphoranes.
abstract: Prior evidence supporting the direct observation of phosphorane intermediates in enzymatic phosphoryl transfer reactions was based on the interpretation of electron density corresponding to trigonal species bridging the donor and acceptor atoms. Close examination of the crystalline state of beta-phosphoglucomutase, the archetypal phosphorane intermediate-containing enzyme, reveals that the trigonal species is not PO-3 , but is MgF-3 (trifluoromagnesate). Although MgF-3 complexes are transition state analogues rather than phosphoryl group transfer reaction intermediates, the presence of fluorine nuclei in near-transition state conformations offers new opportunities to explore the nature of the interactions, in particular the independent measures of local electrostatic and hydrogen-bonding distributions using 19F NMR. Measurements on three beta-PGM-MgF-3 -sugar phosphate complexes show a remarkable relationship between NMR chemical shifts, primary isotope shifts, NOEs, cross hydrogen bond F...H-N scalar couplings, and the atomic positions determined from the high-resolution crystal structure of the beta-PGM-MgF--3 -G6P complex. The measurements provide independent validation of the structural and isoelectronic MgF--3 model of near-transition state conformations.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Baxter
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Bowler
authors.forename: Tooba
authors.initials: T
authors.lastname: Alizadeh
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Cliff
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Hounslow
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.forename: David B
authors.initials: DB
authors.lastname: Berkowitz
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Williams
authors.forename: G Michael
authors.initials: GM
authors.lastname: Blackburn
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Waltho
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005459:Fluorides / Q000737:chemistry* / Q000378:metabolism; D005958:Glucosephosphates / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D017616:Magnesium Compounds / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D010733:Phosphoglucomutase / Q000737:chemistry* / Q000378:metabolism; D010753:Phosphoranes / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D005958:Glucosephosphates; D017616:Magnesium Compounds; D010710:Phosphates; D010753:Phosphoranes; D010733:Phosphoglucomutase; D005459:Fluorides