The molecular structure and catalytic mechanism of a quorum-quenching N-acyl-L-homoserine lactone hydrolase.
In many Gram-negative bacteria, including a number of pathogens such as Pseudomonas aeruginosa and Erwinia carotovora, virulence factor production and biofilm formation are linked to the quorum-sensing systems that use diffusible N-acyl-L-homoserine lactones (AHLs) as intercellular messenger molecules. A number of organisms also contain genes coding for lactonases that hydrolyze AHLs into inactive products, thereby blocking the quorum-sensing systems. Consequently, these enzymes attract intense interest for the development of antiinfection therapies. However, the catalytic mechanism of AHL-lactonase is poorly understood and subject to controversy. We here report a 2.0-angstroms resolution structure of the AHL-lactonase from Bacillus thuringiensis and a 1.7-angstroms crystal structure of its complex with L-homoserine lactone. Despite limited sequence similarity, the enzyme shows remarkable structural similarities to glyoxalase II and RNase Z proteins, members of the metallo-beta-lactamase superfamily. We present experimental evidence that AHL-lactonase is a metalloenzyme containing two zinc ions involved in catalysis, and we propose a catalytic mechanism for bacterial metallo-AHL-lactonases.
Kim
Myung Hee
MH
Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejon 305-600, Korea.
Choi
Won-Chan
WC
Kang
Hye Ok
HO
Lee
Jong Suk
JS
Kang
Beom Sik
BS
Kim
Kyung-Jin
KJ
Derewenda
Zygmunt S
ZS
Oh
Tae-Kwang
TK
Lee
Choong Hwan
CH
Lee
Jung-Kee
JK
D001413:Bacillus thuringiensis / Q000201:enzymology* / Q000235:genetics; D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D002413:Cations, Divalent / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
D002413:Cations, Divalent; D002265:Carboxylic Ester Hydrolases; C432003:N-acyl homoserine lactonase; D015032:Zinc