2baa

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

spinqualitylabelsall models 2baa, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2baa is a 1 chain structure with sequence from Hordeum vulgare. This structure supersedes the now removed PDB entry 1baa. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.8Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CHI2_HORVU Defense against chitin containing fungal pathogens. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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. The refined crystal structure of an endochitinase from Hordeum vulgare L. seeds at 1.8 A resolution.,Hart PJ, Pfluger HD, Monzingo AF, Hollis T, Robertus JD J Mol Biol. 1995 Apr 28;248(2):402-13. PMID:7739049 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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