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PDBsum entry 4j5h
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Hydrolase/hydrolase substrate
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PDB id
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4j5h
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References listed in PDB file
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Key reference
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Title
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A phenylalanine clamp controls substrate specificity in the quorum-Quenching metallo-γ-Lactonase from bacillus thuringiensis.
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Authors
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C.F.Liu,
D.Liu,
J.Momb,
P.W.Thomas,
A.Lajoie,
G.A.Petsko,
W.Fast,
D.Ringe.
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Ref.
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Biochemistry, 2013,
52,
1603-1610.
[DOI no: ]
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PubMed id
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Abstract
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Autoinducer inactivator A (AiiA) is a metal-dependent N-acyl homoserine lactone
hydrolase that displays broad substrate specificity but shows a preference for
substrates with long N-acyl substitutions. Previously, crystal structures of
AiiA in complex with the ring-opened product N-hexanoyl-l-homoserine revealed
binding interactions near the metal center but did not identify a binding pocket
for the N-acyl chains of longer substrates. Here we report the crystal structure
of an AiiA mutant, F107W, determined in the presence and absence of
N-decanoyl-l-homoserine. F107 is located in a hydrophobic cavity adjacent to the
previously identified ligand binding pocket, and the F107W mutation results in
the formation of an unexpected interaction with the ring-opened product.
Notably, the structure reveals a previously unidentified hydrophobic binding
pocket for the substrate's N-acyl chain. Two aromatic residues, F64 and F68,
form a hydrophobic clamp, centered around the seventh carbon in the
product-bound structure's decanoyl chain, making an interaction that would also
be available for longer substrates, but not for shorter substrates. Steady-state
kinetics using substrates of various lengths with AiiA bearing mutations at the
hydrophobic clamp, including insertion of a redox-sensitive cysteine pair,
confirms the importance of this hydrophobic feature for substrate preference.
Identifying the specificity determinants of AiiA will aid the development of
more selective quorum-quenching enzymes as tools and as potential therapeutics.
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