1LQ2

Crystal structure of barley beta-D-glucan glucohydrolase isoenzyme Exo1 in complex with gluco-phenylimidazole


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.210 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Three-dimensional Structure of the Barley {beta}-D-Glucan Glucohydrolase in Complex with a Transition State Mimic.

Hrmova, M.De Gori, R.Smith, B.J.Vasella, A.Varghese, J.N.Fincher, G.B.

(2004) J.Biol.Chem. 279: 4970-4980

  • DOI: 10.1074/jbc.M307188200

  • PubMed Abstract: 
  • Glucophenylimidazole (PheGlcIm), a tetrahydroimidazopyridine-type inhibitor and 4H3 conformer mimic of a glucoside, binds very tightly to a barley beta-d-glucan glucohydrolase, with a Ki constant of 2 x 10(-9) m and a DeltaG of 51 kJ mol(-1). PheGlcI ...

    Glucophenylimidazole (PheGlcIm), a tetrahydroimidazopyridine-type inhibitor and 4H3 conformer mimic of a glucoside, binds very tightly to a barley beta-d-glucan glucohydrolase, with a Ki constant of 2 x 10(-9) m and a DeltaG of 51 kJ mol(-1). PheGlcIm binds to the barley beta-d-glucan glucohydrolase approximately 2 x 10(5) times tighter than laminarin, which is the best non-synthetic ground-state substrate found so far for this enzyme, 10(6) times tighter than 4-nitrophenyl beta-d-glucopyranoside, and 2 x 10(7) tighter than glucose. The three-dimensional structure of the beta-d-glucan glucohydrolase with bound PheGlcIm indicates that the complex resembles a hypothetical transition state during the hydrolytic cycle, that the enzyme derives substrate binding energy from the "aglycone" portion of the ligand, and that it also reveals an anti-protonation trajectory for hydrolysis. Continuous electron densities at the 1.6 sigma level form between the three active site residues Asp95, His207, and Asp285, and the C6OH, C7OH, C8OH, and C9OH groups of PheGlcIm. These electron densities correspond to the most favorable interactions in the three-dimensional structure of the beta-d-glucan glucohydrolase-PheGlcIm complex and indicate atomic distances equal to or less than 2.55 A. The crystallographic data were corroborated with ab initio molecular orbital calculations. The data indicate that the 4E conformation of the glucose part of PheGlcIm is critical for tight binding and provide the first evidence for probable substrate distortion during catalysis by this enzyme.


    Organizational Affiliation

    Faculty of Sciences, School of Agriculture and Wine, University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia. maria.hrmova@adelaide.edu.au




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-D-glucan glucohydrolase isoenzyme Exo1
A
602Hordeum vulgare subsp. vulgareMutation(s): 0 
Find proteins for Q9XEI3 (Hordeum vulgare subsp. vulgare)
Go to UniProtKB:  Q9XEI3
Small Molecules
Ligands 6 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GOL
Query on GOL

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A
GLYCEROL
GLYCERIN; PROPANE-1,2,3-TRIOL
C3 H8 O3
PEDCQBHIVMGVHV-UHFFFAOYSA-N
 Ligand Interaction
MAN
Query on MAN

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A
ALPHA-D-MANNOSE
C6 H12 O6
WQZGKKKJIJFFOK-PQMKYFCFSA-N
 Ligand Interaction
FUC
Query on FUC

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A
ALPHA-L-FUCOSE
C6 H12 O5
SHZGCJCMOBCMKK-SXUWKVJYSA-N
 Ligand Interaction
BMA
Query on BMA

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A
BETA-D-MANNOSE
C6 H12 O6
WQZGKKKJIJFFOK-RWOPYEJCSA-N
 Ligand Interaction
IDD
Query on IDD

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A
(5R,6R,7S,8S)-5-(HYDROXYMETHYL)-2-PHENYL-5,6,7,8-TETRAHYDROIMIDAZO[1,2-A]PYRIDINE-6,7,8-TRIOL
GLUCO-PHENYLIMIDAZOLE
C14 H16 N2 O4
DLVNFMROYKHANV-FVCCEPFGSA-N
 Ligand Interaction
NAG
Query on NAG

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A
N-ACETYL-D-GLUCOSAMINE
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
IDDKi: 1.7 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.210 
  • Space Group: P 43 21 2
Unit Cell:
Length (Å)Angle (°)
a = 100.693α = 90.00
b = 100.693β = 90.00
c = 182.676γ = 90.00
Software Package:
Software NamePurpose
CNSphasing
SCALEPACKdata scaling
CNSrefinement
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-11-18
    Type: Initial release
  • Version 1.1: 2008-04-28
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Non-polymer description, Version format compliance