2BAA

THE REFINED CRYSTAL STRUCTURE OF AN ENDOCHITINASE FROM HORDEUM VULGARE L. SEEDS TO 1.8 ANGSTROMS RESOLUTION


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.8 Å
  • R-Value Work: 0.180 

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This is version 1.2 of the entry. See complete history

Literature

The refined crystal structure of an endochitinase from Hordeum vulgare L. seeds at 1.8 A resolution.

Hart, P.J.Pfluger, H.D.Monzingo, A.F.Hollis, T.Robertus, J.D.

(1995) J.Mol.Biol. 248: 402-413


  • PubMed Abstract: 
  • Class II chitinases (EC 3.2.1.14) are plant defense proteins. They hydrolyze chitin, an insoluble beta-1,4-linked polymer of N-acetylglucosamine (NAG), which is a major cell-wall component of many fungal hyphae. We previously reported the three-dimen ...

    Class II chitinases (EC 3.2.1.14) are plant defense proteins. They hydrolyze chitin, an insoluble beta-1,4-linked polymer of N-acetylglucosamine (NAG), which is a major cell-wall component of many fungal hyphae. We previously reported the three-dimensional structure of the 26 kDa class II endochitinase from barley seeds at 2.8 A resolution, determined using multiple isomorphous replacement (MIR) methods. Here, we report the crystallographic refinement of this chitinase structure against data to 1.8 A resolution using rounds of hand rebuilding coupled with molecular dynamics (X-PLOR). The final model has an R-value of 18.1% for the 5.0 to 1.8 A data shell and 19.8% for the 10.0 to 1.8 A shell, and root-mean-square deviations from standard bond lengths and angles of 0.017 A and 2.88 degrees, respectively. The 243 residue molecule has one beta-sheet, ten alpha-helices and three disulfide bonds; 129 water molecules are included in the final model. We show structural comparisons confirming that chitinase secondary structure resembles lysozyme at the active site region. Based on substrate binding to lysozyme, we have built a hypothetical model for the binding of a hexasaccharide into the pronounced active site cleft of chitinase. This provides the first view of likely substrate interactions from this family of enzymes; the model is consistent with a lysozyme-like mechanism of action in which Glu67 acts as proton donor and Glu89 is likely to stabilize the transition state oxycarbonium ion. These binding site residues, and many hydrophobic residues are conserved in a range of plant chitinases. This endochitinase structure will serve as a model for other plant chitinases, and that catalytic models based on this structure will be applicable to the entire enzyme family.


    Related Citations: 
    • Crystal Structure of an Endochitinase from Hordeum Vulgare L. Seeds
      Hart, P.J.,Monzingo, A.F.,Ready, M.P.,Ernst, S.R.,Robertus, J.D.
      (1993) J.Mol.Biol. 229: 189
    • Crystallization of an Endochitinase from Hordeum Vulgare L. Seeds
      Hart, P.J.,Ready, M.P.,Robertus, J.D.
      (1992) J.Mol.Biol. 225: 565
    • Biochemical and Molecular Characterization of Three Barley Seed Proteins with Antifungal Properties
      Leah, R.,Tommerup, H.,Svendsen, I.,Mundy, J.
      (1991) J.Biol.Chem. 266: 1564


    Organizational Affiliation

    Department of Chemistry and Biochemistry, University of Texas, Austin 78712, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
ENDOCHITINASE (26 KD)
A
243Hordeum vulgareMutation(s): 0 
EC: 3.2.1.14
Find proteins for P23951 (Hordeum vulgare)
Go to UniProtKB:  P23951
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.8 Å
  • R-Value Work: 0.180 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 41.500α = 90.00
b = 64.500β = 108.00
c = 43.100γ = 90.00
Software Package:
Software NamePurpose
X-PLORphasing
X-PLORmodel building
X-PLORrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1996-01-15
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance