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PDBsum entry 4fng
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References listed in PDB file
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Key reference
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Title
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Structure and function of an insect α-Carboxylesterase (αesterase7) associated with insecticide resistance.
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Authors
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C.J.Jackson,
J.W.Liu,
P.D.Carr,
F.Younus,
C.Coppin,
T.Meirelles,
M.Lethier,
G.Pandey,
D.L.Ollis,
R.J.Russell,
M.Weik,
J.G.Oakeshott.
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Ref.
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Proc Natl Acad Sci U S A, 2013,
110,
10177-10182.
[DOI no: ]
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PubMed id
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Abstract
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Insect carboxylesterases from the αEsterase gene cluster, such as αE7 (also
known as E3) from the Australian sheep blowfly Lucilia cuprina (LcαE7), play an
important physiological role in lipid metabolism and are implicated in the
detoxification of organophosphate (OP) insecticides. Despite the importance of
OPs to agriculture and the spread of insect-borne diseases, the molecular basis
for the ability of α-carboxylesterases to confer OP resistance to insects is
poorly understood. In this work, we used laboratory evolution to increase the
thermal stability of LcαE7, allowing its overexpression in Escherichia coli and
structure determination. The crystal structure reveals a canonical
α/β-hydrolase fold that is very similar to the primary target of OPs
(acetylcholinesterase) and a unique N-terminal α-helix that serves as a
membrane anchor. Soaking of LcαE7 crystals in OPs led to the capture of a
crystallographic snapshot of LcαE7 in its phosphorylated state, which allowed
comparison with acetylcholinesterase and rationalization of its ability to
protect insects against the effects of OPs. Finally, inspection of the active
site of LcαE7 reveals an asymmetric and hydrophobic substrate binding cavity
that is well-suited to fatty acid methyl esters, which are hydrolyzed by the
enzyme with specificity constants (∼10(6) M(-1) s(-1)) indicative of a natural
substrate.
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