Mechanism of the quorum-quenching lactonase (AiiA) from Bacillus thuringiensis. 1. Product-bound structures.
Enzymes capable of hydrolyzing N-acyl- l-homoserine lactones (AHLs) used in some bacterial quorum-sensing pathways are of considerable interest for their ability to block undesirable phenotypes. Most known AHL hydrolases that catalyze ring opening (AHL lactonases) are members of the metallo-beta-lactamase enzyme superfamily and rely on a dinuclear zinc site for catalysis and stability. Here we report the three-dimensional structures of three product complexes formed with the AHL lactonase from Bacillus thuringiensis. Structures of the lactonase bound with two different concentrations of the ring-opened product of N-hexanoyl- l-homoserine lactone are determined at 0.95 and 1.4 A resolution and exhibit different product configurations. A structure of the ring-opened product of the non-natural N-hexanoyl- l-homocysteine thiolactone at 1.3 A resolution is also determined. On the basis of these product-bound structures, a substrate-binding model is presented that differs from previous proposals. Additionally, the proximity of the product to active-site residues and observed changes in protein conformation and metal coordination provide insight into the catalytic mechanism of this quorum-quenching metalloenzyme.
Liu
Dali
D
Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
Momb
Jessica
J
Thomas
Pei W
PW
Moulin
Aaron
A
Petsko
Gregory A
GA
Fast
Walter
W
Ringe
Dagmar
D
D001413:Bacillus thuringiensis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D053038:Quorum Sensing
D001426:Bacterial Proteins; D002265:Carboxylic Ester Hydrolases; C432003:N-acyl homoserine lactonase