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PDBsum entry 2oqw
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References listed in PDB file
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Key reference
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Title
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Activation of inhibitors by sortase triggers irreversible modification of the active site.
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Authors
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A.W.Maresso,
R.Wu,
J.W.Kern,
R.Zhang,
D.Janik,
D.M.Missiakas,
M.E.Duban,
A.Joachimiak,
O.Schneewind.
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Ref.
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J Biol Chem, 2007,
282,
23129-23139.
[DOI no: ]
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PubMed id
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Abstract
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Sortases anchor surface proteins to the cell wall of Gram-positive pathogens
through recognition of specific motif sequences. Loss of sortase leads to large
reductions in virulence, which identifies sortase as a target for the
development of antibacterials. By screening 135,625 small molecules for
inhibition, we report here that aryl (beta-amino)ethyl ketones inhibit sortase
enzymes from staphylococci and bacilli. Inhibition of sortases occurs through an
irreversible, covalent modification of their active site cysteine. Sortases
specifically activate this class of molecules via beta-elimination, generating a
reactive olefin intermediate that covalently modifies the cysteine thiol.
Analysis of the three-dimensional structure of Bacillus anthracis sortase B with
and without inhibitor provides insights into the mechanism of inhibition and
reveals binding pockets that can be exploited for drug discovery.
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Figure 4.
FIGURE 4. Three-dimensional structure of the active site of
sortase B modified by AAEK1. A, thienylpropanone adduct to
sortase Cys-233 (blue), the product of the reaction of sortase B
with AAEK1, is compared with the sortase B structure at 1.6
Å (orange). The adduct occupies the position of three
water molecules (orange spheres) and is stacking against
Tyr-138. B, the catalytic triad of sortase B (His140, Asp-234,
and Cys-233) and Arg-243 are in close proximity to the inhibitor
adduct and undergo substantial structural shifts. The SrtB
(green) and SrtB-AAEK adduct (blue) are superimposed. The figure
was generated using PyMOL^TM. C, thienylpropanone modification
of the active site of sortase. Electron density map of the B.
anthracis sortase B-AAEK1 adduct demonstrating Cys-233, Tyr-138,
and the thienylpropanone. Green, sulfur; red, oxygen. The figure
was generated using COOT.
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Figure 7.
FIGURE 7. Model for the mechanism of inhibition of sortase
by AAEKs. Deprotonation of the  carbon is conjectured
to occur via a base in the active site of sortase. This
generates enolate 13, which may be stabilized in a manner
similar to the oxyanion intermediate of sortase during catalysis
(e.g. by the guanidinium of a conserved active site arginine).
This intermediate eliminates an amine, here dimethylamine, from
the  -position to generate
14. The electrophilic nature of 14 allows it to serve as an
acceptor in a Michael-type conjugate addition by the thiol of
the active site cysteine. This resulting enolate might also be
stabilized by the guanidinium moiety; subsequent protonation by
enzyme or medium would then generate the stable AAEK thioether
adduct observed.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
23129-23139)
copyright 2007.
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