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PDBsum entry 3ee5
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References listed in PDB file
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Key reference
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Title
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Deoxygenated disaccharide analogs as specific inhibitors of beta1-4-Galactosyltransferase 1 and selectin-Mediated tumor metastasis.
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Authors
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J.R.Brown,
F.Yang,
A.Sinha,
B.Ramakrishnan,
Y.Tor,
P.K.Qasba,
J.D.Esko.
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Ref.
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J Biol Chem, 2009,
284,
4952-4959.
[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 have
been manually determined.
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Abstract
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The disaccharide peracetylated GlcNAcbeta1-3Galbeta-O-naphthalenemethanol
(disaccharide 1) diminishes the formation of the glycan sialyl Lewis X
(Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3) GlcNAc; sLe(X)) in tumor cells. Previous
studies showed that the mechanism of action of disaccharide 1 involves three
steps: (i) deacetylation by carboxyesterases, (ii) action as a biosynthetic
intermediate for downstream enzymes involved in sLe(X) assembly, and (iii)
generation of several glycans related to sLe(X). In this report, we show that
GlcNAcbeta1-3Galbeta-O-naphthalenemethanol binds to the acceptor site of human
beta1-4-galactosyltransferase much like the acceptor trisaccharide,
GlcNAcbeta1-2Manbeta1-6Man, which is present on N-linked glycans. The 4'-deoxy
analog, in which the acceptor hydroxyl group was replaced by -H, did not act as
a substrate but instead acted as a competitive inhibitor of the enzyme. The
acetylated form of this compound inhibited sLe(X) formation in U937 monocytic
leukemia cells, suggesting that it had inhibitory activity in vivo as well. A
series of synthetic acetylated analogs of 1 containing -H, -F, -N(3), -NH(2), or
-OCH(3) instead of the hydroxyl groups at C-3'- and C-4'-positions of the
terminal N-acetylglucosamine residue also blocked sLe(X) formation in cells. The
reduction of sLe(X) by the 4'-deoxy analog also diminished experimental tumor
metastasis by Lewis lung carcinoma in vivo. These data suggest that nonsubstrate
disaccharides have therapeutic potential through their ability to bind to
glycosyltransferases in vivo and to alter glycan-dependent pathologic processes.
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Figure 1.
Chemical structure of per-O-acetylated
GlcNAcβ1–3Galβ-O-naphthalenemethanol ( 1 ) and C-3′ and
C-4′ hydroxyl-modified analogs ( 2 – 9 ).
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Figure 2.
Co-crystallization of deacetylated 1 with the open form of
the human enzyme, hM340H-Gal-T1. a, binding of deacetylated 1 to
the catalytic domain of β4Gal-T1, in the presence of Mn^2+
(purple sphere) and UDP-hexanolamine (UDP-H). The β4Gal-T1
molecule is found in the closed conformation with its Trp-310
side chain (red) placed inside the catalytic pocket, interacting
with the phosphate oxygen atom of UDP-hexanolamine molecule,
whereas the long flexible loop (blue) covers the
UDP-hexanolamine and exposes the acceptor binding site to
facilitate binding to the enzyme. b, the molecular interactions
of deacetylated 1 (blue) with the β4Gal-T1 (green). The
hydrogen bonds are shown in black dotted lines. The GlcNAc
moiety of deacetylated 1 is bound in the acceptor sugar binding
site. The Gal residue forms hydrophobic interactions with the
aromatic side chain of the Tyr-282 residue, whereas the
naphthalenemethanol extends out of the sugar binding site,
weakly interacting with the β4Gal-T1 molecule. There is a
structural water molecule (W) indicated with black dotted lines
that, in addition to forming a hydrogen bond with the side-chain
amino group of Arg-355, bridges the GlcNAc and Gal via hydrogen
bonds. c, molecular surface (van der Waals) diagram showing the
binding of deacetylated trisaccharide
GlcNAcβ1–2Manα1–6Manβ-O-R (where R represents
-CH[2]–CH[2]–CH[2]–CH=CH[2] (15)) to β4Gal-T1 (light
blue). d, molecular surface (van der Waals) diagram showing the
binding of deacetylated disaccharide 1 to β4Gal-T1 (light
blue). e, superposition of the bound deacetylated disaccharide 1
(blue) with the bound trisaccharide,
GlcNAcβ1–2Manα1–6Manβ-O-R (yellow) in the respective
acceptor substrate complexes with β4Gal-T1 (blue).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2009,
284,
4952-4959)
copyright 2009.
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