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PDBsum entry 3lsd
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Sugar binding protein
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PDB id
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3lsd
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References listed in PDB file
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Key reference
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Title
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N-Domain of human adhesion/growth-Regulatory galectin-9: preference for distinct conformers and non-Sialylated n-Glycans and detection of ligand-Induced structural changes in crystal and solution.
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Authors
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D.Solís,
M.J.Maté,
M.Lohr,
J.P.Ribeiro,
L.López-Merino,
S.André,
E.Buzamet,
F.J.Cañada,
H.Kaltner,
M.Lensch,
F.M.Ruiz,
G.Haroske,
U.Wollina,
M.Kloor,
J.Kopitz,
J.L.Sáiz,
M.Menéndez,
J.Jiménez-Barbero,
A.Romero,
H.J.Gabius.
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Ref.
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Int J Biochem Cell Biol, 2010,
42,
1019-1029.
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PubMed id
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Abstract
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Human tandem-repeat-type galectin-9 is a potent adhesion/growth-regulatory
effector via lectin capacity of its N- and C-terminal domains. This bioactivity
prompted further crystallographic study of the N-domain, combined with analysis
in solution. Binding of lactose markedly increased the N-domain's resistance to
thermal denaturation. Crystallography revealed its intimate contact profile,
besides detecting an extension of the beta-sandwich fold by an antiparallel
beta-strand F0 aligned to the C-terminal F1 strand. Ligand accommodation in its
low-energy conformation leads to a movement of Arg87's side chain. As
consequence, the ligand's glucose moiety and Arg87 become hydrogen bonded. The
resulting predictions for spatial parameters in solution were verified by
determining (a) the pattern of magnetization transfer from the protein to
protons of lactose and Forssman disaccharide by NMR spectroscopy and (b) the
ellipticity changes at wavelengths characteristic for Trp/Tyr residues in
near-UV CD spectroscopy. Whereas solid-phase assays confirmed a previously noted
tendency for homo- and heterotypic aggregation, gel filtration and
ultracentrifugation disclosed monomeric status in solution, in line with
crystallographic data. Using cell mutants with defects in glycosylation, this
lectin domain was shown to preferentially bind N-glycans without
alpha2,3-sialylation. Since proximal promoter sequences were delineated to
diverge markedly among galectin genes and resulting differences in expression
profiles were exemplarily documented immunohistochemically, the intrafamily
diversification appears to have assigned this protein to a characteristic
expression and activity profile among galectins. Our data thus take the
crystallographic information to the level of the lectin in solution and in
tissues by a strategic combination of spectroscopic and cell/histochemical
assays.
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