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PDBsum entry 2jcl
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References listed in PDB file
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Key reference
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Title
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Conformational changes induced by binding udp-2f-Galactose to alpha-1,3 galactosyltransferase- Implications for catalysis.
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Authors
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H.Jamaluddin,
P.Tumbale,
S.G.Withers,
K.R.Acharya,
K.Brew.
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Ref.
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J Mol Biol, 2007,
369,
1270-1281.
[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
94%.
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Abstract
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Alpha-1,3 galactosyltransferase (alpha3GT) catalyzes the transfer of galactose
from UDP-galactose to beta-linked galactosides with retention of its alpha
configuration. Although several complexes of alpha3GT with inhibitors and
substrates have been reported, no structure has been determined of a complex
containing intact UDP-galactose. We describe the structure of a complex
containing an inhibitory analogue of UDP-galactose, UDP-2F-galactose, in a
complex with the Arg365Lys mutant of alpha3GT. The inhibitor is bound in a
distorted, bent configuration and comparison with the structure of the apo form
of this mutant shows that the interaction induces structural changes in the
enzyme, implying a role for ground state destabilization in catalysis. In
addition to a general reduction in flexibility in the enzyme indicated by a
large reduction in crystallographic B-factors, two loops, one centred around
Trp195 and one encompassing the C-terminal 11 residues undergo large structural
changes in complexes with UDP and UDP derivatives. The distorted configuration
of the bound UDP-2F-galactose in its complex is stabilized, in part, by
interactions with residues that are part of or near the flexible loops.
Mutagenesis and truncation studies indicate that two highly conserved basic
amino acid residues in the C-terminal region, Lys359 and Arg365 are important
for catalysis, probably reflecting their roles in these ligand-mediated
conformational changes. A second Mn(2+) cofactor has been identified in the
catalytic site of a complex of the Arg365Lys with UDP, in a location that
suggests it could play a role in facilitating UDP release, consistent with
kinetic studies that show alpha3GT activity depends on the binding of two
manganese ions. Conformational changes in the C-terminal 11 residues require an
initial reorganization of the Trp195 loop and are linked to enzyme progress
through the catalytic cycle, including donor substrate distortion, cleavage of
the UDP-galactose bond, galactose transfer, and UDP release.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2007,
369,
1270-1281)
copyright 2007.
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