3WKZ: Crystal Structure Of The Ostrinia Furnacalis Group I Chitinase Catalytic Domain E148q Mutant

Citation:
Abstract
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 A. 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.
PDB ID: 3WKZDownload
MMDB ID: 118954
PDB Deposition Date: 2013/11/5
Updated in MMDB: 2015/04
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Similar Structures:
Biological Unit for 3WKZ: monomeric; determined by author and by software (PISA)
Molecular Components in 3WKZ
Label Count Molecule
Protein (1 molecule)
1
Chitinase
Molecule annotation
Chemicals (2 molecules)
1
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
.