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PDBsum entry 1jot
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Structure of the complex of maclura pomifera agglutinin and the t-Antigen disaccharide, Galbeta1,3galnac.
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Authors
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X.Lee,
A.Thompson,
Z.Zhang,
H.Ton-That,
J.Biesterfeldt,
C.Ogata,
L.Xu,
R.A.Johnston,
N.M.Young.
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Ref.
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J Biol Chem, 1998,
273,
6312-6318.
[DOI no: ]
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PubMed id
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Abstract
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Maclura pomifera agglutinin is a tetrameric plant seed lectin with high affinity
for the tumor-associated T-antigen disaccharide, Galbeta1,3GalNAcalpha, and
hence for many O-linked glycopeptide structures. Unlike members of most lectin
families, it lacks both metal ions and Cys residues. The structure of its
complex with Galbeta1,3GalNAc was determined to 2.2 by first using
multiwavelength anomalous diffraction with a lead derivative of the native
protein, and then using molecular replacement with the unrefined structure as a
model to solve the structure of the complex. The subunits share the beta-prism
architecture and three-fold pseudo-symmetry of the related lectin jacalin, with
the 21-residue beta-chains in the center of the tetramer. Interactions with the
GalNAc predominate in the binding of the disaccharide. It forms a network of
H-bonds with only one side chain, from an Asp residue, the amino group of the
N-terminal Gly of the alpha-chain, and peptide backbone atoms of two aromatic
residues. The Gal moiety does not H-bond directly with residues in the same
monomer, i.e. there is no true subsite for it, but there are interactions
through two water molecules. In the crystal, it interacts with residues in the
binding site of an adjacent tetramer. The minimum energy conformation expected
for the disaccharide is retained, despite its mediating the tetramer-tetramer
interactions in the crystal packing. The resulting lattice is comparable to
those seen for complexes of other lectins with branched glycopeptides.
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Figure 3.
Fig. 3. Backbone structure of the tetramer with the bound
ligand. The Greek key subdomains of each monomer are shown in
red, green, and purple with the  -chain in
blue (see Fig. 4). This figure and Figs. 4 and 5 were prepared
with MOLSCRIPT (21) and^ RASTER 3D (22).
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Figure 6.
Fig. 6. Hydrogen-bonding scheme for the MPA-disaccharide
complex. The two charged groups of Gly-1 and Asp-125 form most
of^ the H-bonds, to the GalNAc. The remaining H-bonds are from
backbone^ atoms plus two water molecules, one of which forms the
only H-bond^ to the Gal.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(1998,
273,
6312-6318)
copyright 1998.
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