 |
PDBsum entry 1knm
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
High-Resolution crystal structures of the lectin-Like xylan binding domain from streptomyces lividans xylanase 10a with bound substrates reveal a novel mode of xylan binding.
|
|
|
Authors
|
|
V.Notenboom,
A.B.Boraston,
S.J.Williams,
D.G.Kilburn,
D.R.Rose.
|
|
|
Ref.
|
|
Biochemistry, 2002,
41,
4246-4254.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Carbohydrate-binding module (CBM) family 13 includes the "R-type" or "ricin
superfamily" beta-trefoil lectins. The C-terminal CBM, CBM13, of xylanase 10A
from Streptomyces lividans is a family 13 CBM that is not only structurally
similar to the "R-type" lectins but also somewhat functionally similar. The
primary function of CBM13 is to bind the polysaccharide xylan, but it retains
the ability of the R-type lectins to bind small sugars such as lactose and
galactose. The association of CBM13 with xylan appears to involve cooperative
and additive participation of three binding pockets in each of the three trefoil
domains of CBM13, suggesting a novel mechanism of CBM-xylan interaction. Thus,
the interaction of CBM13 with sugars displays considerable plasticity for which
we provide a structural rationale. The high-resolution crystal structure of
CBM13 was determined by multiple anomalous dispersion from a complex of CBM13
with a brominated ligand. Crystal structures of CBM13 in complex with lactose
and xylopentaose revealed two distinct mechanisms of ligand binding. CBM13 has
retained its specificity for lactose via Ricin-like binding in all of the three
classic trefoil binding pockets. However, CBM13 has the ability to bind either
the nonreducing galactosyl moiety or the reducing glucosyl moiety of lactose.
The mode of xylopentaose binding suggests adaptive mutations in the trefoil
sugar binding scaffold to accommodate internal binding on helical polymers of
xylose.
|
|
|
|
|
|
|
