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PDBsum entry 1w6m
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Sugar binding protein
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PDB id
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1w6m
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References listed in PDB file
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Key reference
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Title
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Growth-Regulatory human galectin-1: crystallographic characterisation of the structural changes induced by single-Site mutations and their impact on the thermodynamics of ligand binding.
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Authors
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M.F.López-Lucendo,
D.Solís,
S.André,
J.Hirabayashi,
K.Kasai,
H.Kaltner,
H.J.Gabius,
A.Romero.
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Ref.
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J Mol Biol, 2004,
343,
957-970.
[DOI no: ]
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PubMed id
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Abstract
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Human galectin-1 is a potent multifunctional effector that participates in
specific protein-carbohydrate and protein-protein (lipid) interactions. By
determining its X-ray structure, we provide the basis to define the structure of
its ligand-binding pocket and to perform rational drug design. We have also
analysed whether single-site mutations introduced at some distance from the
carbohydrate recognition domain can affect the lectin fold and influence sugar
binding. Both the substitutions introduced in the C2S and R111H mutants altered
the presentation of the loop, harbouring Asp123 in the common
"jelly-roll" fold. The orientation of the side-chain was inverted 180
degrees and the positions of two key residues in the sugar-binding site of the
R111H mutant were notably shifted, i.e. His52 and Trp68. Titration calorimetry
was used to define the decrease in ligand affinity in both mutants and a
significant increase in the entropic penalty was found to outweigh a slight
enhancement of the enthalpic contribution. The position of the SH-groups in the
galectin appeared to considerably restrict the potential to form intramolecular
disulphide bridges and was assumed to be the reason for the unstable lectin
activity in the absence of reducing agent. However, this offers no obvious
explanation for the improved stability of the C2S mutant under oxidative
conditions. The noted long-range effects in single-site mutants are relevant for
the functional divergence of closely related galectins and in more general
terms, the functionality definition of distinct amino acids.
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Figure 2.
Figure 2. Ribbon diagram of the homodimeric human
galectin-1 prepared with MOLSCRIPT.70 The b-strands in the
five-stranded (F1-F5) and six-stranded (S1-S6a/S6b) b-sheets are
indicated by the letter-number code.
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Figure 5.
Figure 5. The carbohydrate recognition site of hGal-1. (a)
The binding site in free hGal-1, showing the position of bound
water molecules as green spheres. The three water molecules are
placed at the sites of interaction with the hydroxyl groups O4,
O6 of galactose and O3 of glucose, when the ligand enters the
binding site. (b) A view of the CRD of wt hGal-1 complexed with
lactose. The carbohydrate-binding cleft is discernible in the
concave face of the S4-S6a/S6b b-sheet. The lactose moiety and
the side-chains of the sugar-binding residues are shown as
stick-and-ball models.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2004,
343,
957-970)
copyright 2004.
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