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PDBsum entry 1lu1
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References listed in PDB file
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Key reference
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Title
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Carbohydrate binding, Quaternary structure and a novel hydrophobic binding site in two legume lectin oligomers from dolichos biflorus.
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Authors
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T.W.Hamelryck,
R.Loris,
J.Bouckaert,
M.H.Dao-Thi,
G.Strecker,
A.Imberty,
E.Fernandez,
L.Wyns,
M.E.Etzler.
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Ref.
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J Mol Biol, 1999,
286,
1161-1177.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
percentage match of
96%.
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Abstract
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The seed lectin (DBL) from the leguminous plant Dolichos biflorus has a unique
specificity among the members of the legume lectin family because of its high
preference for GalNAc over Gal. In addition, precipitation of blood group A+H
substance by DBL is slightly better inhibited by a blood group A trisaccharide
(GalNAc(alpha1-3)[Fuc(alpha1-2)]Gal) containing pentasaccharide, and about 40
times better by the Forssman disaccharide (GalNAc(alpha1-3)GalNAc) than by
GalNAc. We report the crystal structures of the DBL-blood group A trisaccharide
complex and the DBL-Forssman disaccharide complex.A comparison with the binding
sites of Gal-binding legume lectins indicates that the low affinity of DBL for
Gal is due to the substitution of a conserved aromatic residue by an aliphatic
residue (Leu127). Binding studies with a Leu127Phe mutant corroborate these
conclusions. DBL has a higher affinity for GalNAc because the N-acetyl group
compensates for the loss of aromatic stacking in DBL by making a hydrogen bond
with the backbone amide group of Gly103 and a hydrophobic contact with the
side-chains of Trp132 and Tyr104. Some legume lectins possess a hydrophobic
binding site that binds adenine and adenine-derived plant hormones, i.e.
cytokinins. The exact function of this binding site is unknown, but
adenine/cytokinin-binding legume lectins might be involved in storage of plant
hormones or plant growth regulation. The structures of DBL in complex with
adenine and of the dimeric stem and leaf lectin (DB58) from the same plant
provide the first structural data on these binding sites. Both oligomers possess
an unusual architecture, featuring an alpha-helix sandwiched between two
monomers. In both oligomers, this alpha-helix is directly involved in the
formation of the hydrophobic binding site. DB58 adopts a novel quaternary
structure, related to the quaternary structure of the DBL heterotetramer, and
brings the number of know legume lectin dimer types to four.
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Figure 3.
Figure 3. The overall structure of the DB58 dimer. The dimer
corresponds to dimer AC in the DBL tetramer (Figure 1(b). Metal
ions as in Figure 1(a).
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Figure 6.
Figure 6. Binding of iodinated lectins (wild-type DBL, WTSL;
native recombinant DBL, Native SL; and the Leu127Phe mutant,
L127F) to hog blood group A+H-Sepharose (BGS-Seph).
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1999,
286,
1161-1177)
copyright 1999.
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