Structural and Biochemical Characterization of AidC, a Quorum-Quenching Lactonase with Atypical Selectivity

Romila Mascarenhas, Pei W. Thomas, Chun Xiang Wu, Boguslaw P. Nocek, Quyen Hoang, Dali Liu, Walter Fast

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Quorum-quenching catalysts are of interest for potential application as biochemical tools for interrogating interbacterial communication pathways, as antibiofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-L-homoserine lactone (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-supplemented AidC is the most efficient wild-type quorum-quenching enzymes characterized to date, with a k<inf>cat</inf>/K<inf>M</inf> value of approximately 2 × 10<sup>6</sup> M<sup>-1</sup> s<sup>-1</sup> for N-heptanoyl-L-homoserine lactone. The enzyme has stricter substrate selectivity and significantly lower K<inf>M</inf> values (ca. 50 μM for preferred substrates) compared to those of typical AHL lactonases (ca. >1 mM). X-ray crystal structures of AidC alone and with the product N-hexanoyl-l-homoserine were determined at resolutions of 1.09 and 1.67 Å, respectively. Each structure displays as a dimer, and dimeric oligiomerization was also observed in solution by size-exclusion chromatography coupled with multiangle light scattering. The structures reveal two atypical features as compared to previously characterized AHL lactonases: a "kinked" α-helix that forms part of a closed binding pocket that provides affinity and enforces selectivity for AHL substrates and an active-site His substitution that is usually found in a homologous family of phosphodiesterases. Implications for the catalytic mechanism of AHL lactonases are discussed. (Figure Presented).

Original languageEnglish
Pages (from-to)4342-4353
Number of pages12
JournalBiochemistry
Volume54
Issue number28
DOIs
StatePublished - Jul 21 2015

Fingerprint

Acyl-Butyrolactones
Quorum Sensing
Catalyst selectivity
Quenching
Chryseobacterium
Homoserine
Substrates
Phosphoric Diester Hydrolases
Enzymes
Anti-Infective Agents
Size exclusion chromatography
Gel Chromatography
Zinc
Catalytic Domain
Dimers
Light scattering
X-Rays
homoserine lactone
Animals
Substitution reactions

ASJC Scopus subject areas

  • Biochemistry

Cite this

Structural and Biochemical Characterization of AidC, a Quorum-Quenching Lactonase with Atypical Selectivity. / Mascarenhas, Romila; Thomas, Pei W.; Wu, Chun Xiang; Nocek, Boguslaw P.; Hoang, Quyen; Liu, Dali; Fast, Walter.

In: Biochemistry, Vol. 54, No. 28, 21.07.2015, p. 4342-4353.

Research output: Contribution to journalArticle

Mascarenhas, Romila ; Thomas, Pei W. ; Wu, Chun Xiang ; Nocek, Boguslaw P. ; Hoang, Quyen ; Liu, Dali ; Fast, Walter. / Structural and Biochemical Characterization of AidC, a Quorum-Quenching Lactonase with Atypical Selectivity. In: Biochemistry. 2015 ; Vol. 54, No. 28. pp. 4342-4353.
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AB - Quorum-quenching catalysts are of interest for potential application as biochemical tools for interrogating interbacterial communication pathways, as antibiofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-L-homoserine lactone (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-supplemented AidC is the most efficient wild-type quorum-quenching enzymes characterized to date, with a kcat/KM value of approximately 2 × 106 M-1 s-1 for N-heptanoyl-L-homoserine lactone. The enzyme has stricter substrate selectivity and significantly lower KM values (ca. 50 μM for preferred substrates) compared to those of typical AHL lactonases (ca. >1 mM). X-ray crystal structures of AidC alone and with the product N-hexanoyl-l-homoserine were determined at resolutions of 1.09 and 1.67 Å, respectively. Each structure displays as a dimer, and dimeric oligiomerization was also observed in solution by size-exclusion chromatography coupled with multiangle light scattering. The structures reveal two atypical features as compared to previously characterized AHL lactonases: a "kinked" α-helix that forms part of a closed binding pocket that provides affinity and enforces selectivity for AHL substrates and an active-site His substitution that is usually found in a homologous family of phosphodiesterases. Implications for the catalytic mechanism of AHL lactonases are discussed. (Figure Presented).

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