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PDBsum entry 2wlc
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References listed in PDB file
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Key reference
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Title
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Structural and kinetic characterizations of the polysialic acid o-Acetyltransferase oatwy from neisseria meningitidis.
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Authors
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H.J.Lee,
B.Rakić,
M.Gilbert,
W.W.Wakarchuk,
S.G.Withers,
N.C.Strynadka.
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Ref.
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J Biol Chem, 2009,
284,
24501-24511.
[DOI no: ]
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PubMed id
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Abstract
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The neuroinvasive pathogen Neisseria meningitidis has 13 capsular serogroups,
but the majority of disease is caused by only 5 of these. Groups B, C, Y, and
W-135 all display a polymeric sialic acid-containing capsule that provides a
means for the bacteria to evade the immune response during infection by
mimicking host sialic acid-containing cell surface structures. These capsules in
serogroups C, Y, and W-135 can be further acetylated by a sialic acid-specific
O-acetyltransferase, a modification that correlates with decreased
immunoreactivity and increased virulence. In N. meningitidis serogroup Y, the
O-acetylation reaction is catalyzed by the enzyme OatWY, which we show has clear
specificity toward the serogroup Y capsule ([Glc-(alpha1-->4)-Sia](n)). To
understand the underlying molecular basis of this process, we have performed
crystallographic analysis of OatWY with bound substrate as well as determined
kinetic parameters of the wild type enzyme and active site mutants. The
structure of OatWY reveals an intimate homotrimer of left-handed beta-helix
motifs that frame a deep active site cleft selective for the polysialic
acid-bearing substrate. Within the active site, our structural, kinetic, and
mutagenesis data support the role of two conserved residues in the catalytic
mechanism (His-121 and Trp-145) and further highlight a significant movement of
Tyr-171 that blocks the active site of the enzyme in its native form.
Collectively, our results reveal the first structural features of a bacterial
sialic acid O-acetyltransferase and provide significant new insight into its
catalytic mechanism and specificity for the capsular polysaccharide of serogroup
Y meningococci.
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Figure 1.
Reaction scheme of the OatWY-catalyzed O-acetyltransferase.
Although acetylation of both the O-7 and O-9 hydroxyl group of
the N. meningitidis serogroup Y polysialic acid has been implied
through NMR analysis of the corresponding bacterial capsule
(11), for simplicity only the O-9 transfer is shown here.
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Figure 5.
Mechanistic scheme of OatWY polysialic acid
acetyltransferase. In the schematic above, the two interacting
subunits, which define a complete active site, are represented
as gray boxes and serve to illustrate the conformational role of
Tyr-171 in allowing access to substrate acetyl-CoA. In the
dotted box below, a proposed mechanistic scheme is shown
highlighting the role of His-121 from one subunit and Trp-145′
from the second subunit that make up the active site.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2009,
284,
24501-24511)
copyright 2009.
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