3W4R image
Deposition Date 2013-01-10
Release Date 2014-02-12
Last Version Date 2024-11-20
Entry Detail
PDB ID:
3W4R
Keywords:
Title:
Crystal structure of an insect chitinase from the Asian corn borer, Ostrinia furnacalis
Biological Source:
Source Organism:
Method Details:
Experimental Method:
Resolution:
1.70 Å
R-Value Free:
0.15
R-Value Work:
0.14
R-Value Observed:
0.14
Space Group:
P 65
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Chitinase
Chain IDs:A
Chain Length:554
Number of Molecules:1
Biological Source:Ostrinia furnacalis
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
ASN A ASN GLYCOSYLATION SITE
Ligand Molecules
Primary Citation
Structural characteristics of an insect group I chitinase, an enzyme indispensable to moulting
Acta Crystallogr.,Sect.D 70 932 942 (2014)
PMID: 24699639 DOI: 10.1107/S1399004713033841

Abstact

Insects possess a greater number of chitinases than any other organisms. This work is the first report of unliganded and oligosaccharide-complexed crystal structures of the insect chitinase OfChtI from Ostrinia furnacalis, which is essential to moulting. The obtained crystal structures were solved at resolutions between 1.7 and 2.2 Å. A structural comparison with other chitinases revealed that OfChtI contains a long substrate-binding cleft similar to the bacterial chitinase SmChiB from Serratia marcescens. However, unlike the exo-acting SmChiB, which has a blocked and tunnel-like cleft, OfChtI possesses an open and groove-like cleft. The complexed structure of the catalytic domain of OfChtI (OfChtI-CAD) with (GlcNAc)2/3 indicates that the reducing sugar at subsite -1 is in an energetically unfavoured `boat' conformation, a state that possibly exists just before the completion of catalysis. Because OfChtI is known to act from nonreducing ends, (GlcNAc)3 would be a hydrolysis product of (GlcNAc)6, suggesting that OfChtI possesses an endo enzymatic activity. Furthermore, a hydrophobic plane composed of four surface-exposed aromatic residues is adjacent to the entrance to the substrate-binding cleft. Mutations of these residues greatly impair the chitin-binding activity, indicating that this hydrophobic plane endows OfChtI-CAD with the ability to anchor chitin. This work reveals the unique structural characteristics of an insect chitinase.

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Primary Citation of related structures