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PDBsum entry 1vrw
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Oxidoreductase
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PDB id
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1vrw
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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 elucidation of the specificity of the antibacterial agent triclosan for malarial enoyl acyl carrier protein reductase.
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Authors
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R.Perozzo,
M.Kuo,
A.S.Sidhu,
J.T.Valiyaveettil,
R.Bittman,
W.R.Jacobs,
D.A.Fidock,
J.C.Sacchettini.
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Ref.
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J Biol Chem, 2002,
277,
13106-13114.
[DOI no: ]
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PubMed id
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Abstract
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The human malaria parasite Plasmodium falciparum synthesizes fatty acids using a
type II pathway that is absent in humans. The final step in fatty acid
elongation is catalyzed by enoyl acyl carrier protein reductase, a validated
antimicrobial drug target. Here, we report the cloning and expression of the P.
falciparum enoyl acyl carrier protein reductase gene, which encodes a 50-kDa
protein (PfENR) predicted to target to the unique parasite apicoplast. Purified
PfENR was crystallized, and its structure resolved as a binary complex with
NADH, a ternary complex with triclosan and NAD(+), and as ternary complexes
bound to the triclosan analogs 1 and 2 with NADH. Novel structural features were
identified in the PfENR binding loop region that most closely resembled
bacterial homologs; elsewhere the protein was similar to ENR from the plant
Brassica napus (root mean square for Calphas, 0.30 A). Triclosan and its analogs
1 and 2 killed multidrug-resistant strains of intra-erythrocytic P. falciparum
parasites at sub to low micromolar concentrations in vitro. These data define
the structural basis of triclosan binding to PfENR and will facilitate
structure-based optimization of PfENR inhibitors.
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Figure 2.
Fig. 2. Tertiary structure of PfENR. a, representation of
subunit B of the PfENR tetramer with the cofactor NADH and
inhibitor triclosan bound to their active sites. Helices are
shown in gold, the  -strands in
green, NADH and triclosan are colored by atom type. The tertiary
structure shows the Rossmann fold typical of
dinucleotide-binding enzymes (43). The chain break visible at
the top of the inhibitor binding site is due to the PfENR
substrate binding loop that was not resolved in the crystal
structures. b, front view of the PfENR tetramer, in which each
subunit is represented as a differently colored tube. The bound
NADH is colored by atom type. Three perpendicular 2-fold
symmetry axes intersect in the center, creating a molecule of
internal 222 symmetry.
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Figure 4.
Fig. 4. Structural details of the substrate/inhibitor
binding site. a, stereo view of the 2F[o]  F[c]
electron density map contoured at 1  for bound
analog 2 and NADH cofactor. Shown are residues 277 and 216-221.
b, stereo view of the three superimposed PfENR·inhibitor
complexes. Residues involved in the formation of the binding
pocket are shown. The most important amino acids for
interactions are labeled. Triclosan is shown in red, 1 in blue,
and 2 in green. The corresponding cofactor of each inhibitor
complex is colored accordingly. Hydrogen bonds with Tyr277 and
the 2'-hydroxyl group of the nicotinamide ribose, as well as
three additional hydrogen bonds mediated through the hydroxyl
group of the naphthalene ring of 2 are shown as yellow dotted
lines. The binding mode of triclosan, 1, and 2 showed the same
stacking interactions to the nicotinamide ring of the cofactor
with respect to ring A. Inhibitor 2 also exhibited three
additional hydrogen bonds mediated through the hydroxyl group of
the naphthalene ring that could interact with the side-chain
nitrogen of Asn218 and the main-chain oxygen and nitrogen of
Ala^219.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
13106-13114)
copyright 2002.
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