The quorum-quenching lactonase from Bacillus thuringiensis is a metalloprotein.
Lactonases from Bacillus species hydrolyze the N-acylhomoserine lactone (AHL) signaling molecules used in quorum-sensing pathways of many Gram-negative bacteria, including Pseudomonas aeruginosa and Erwinia carotovora, both significant pathogens. Because of sequence similarity, these AHL lactonases have been assigned to the metallo-beta-lactamase superfamily of proteins, which includes metalloenzymes of diverse activity, mechanism, and metal content. However, a recent study claims that AHL lactonase from Bacillus sp. 240B1 is not a metalloprotein [Wang, L. H., et al. (2004) J. Biol. Chem. 279, 13645]. Here, the gene for an AHL lactonase from Bacillus thuringiensis is cloned, and the protein is expressed, purified, and found to bind 2 equiv of zinc. The metal-bound form of AHL lactonase catalyzes the hydrolysis of N-hexanoyl-(S)-homoserine lactone but not the (R) enantiomer. Removal of both zinc ions results in loss of activity, and reconstitution with zinc restores activity, indicating the importance of metal ions for catalytic activity. Metal content, sequence alignments, and X-ray absorption spectroscopy of the zinc-containing lactonase all support a proposed dinuclear zinc binding site similar to that found in glyoxalase II.
Thomas
Pei W
PW
Division of Medicinal Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
Stone
Everett M
EM
Costello
Alison L
AL
Tierney
David L
DL
Fast
Walter
W
D000595:Amino Acid Sequence; D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D001413:Bacillus thuringiensis / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D001665:Binding Sites / Q000235:genetics; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D003956:Dialysis; D004789:Enzyme Activation; D007700:Kinetics; D058619:Maltose-Binding Proteins; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D008969:Molecular Sequence Data; D015398:Signal Transduction; D013057:Spectrum Analysis; D014965:X-Rays; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
D001051:Apoenzymes; D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D008667:Metalloproteins; D002265:Carboxylic Ester Hydrolases; C432003:N-acyl homoserine lactonase; D015032:Zinc