 |
PDBsum entry 3w4r
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
Structural characteristics of an insect group i chitinase, An enzyme indispensable to moulting.
|
|
|
Authors
|
|
L.Chen,
T.Liu,
Y.Zhou,
Q.Chen,
X.Shen,
Q.Yang.
|
|
|
Ref.
|
|
Acta Crystallogr D Biol Crystallogr, 2014,
70,
932-942.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
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 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.
|
|
|
|
|
|
|
