AidH, an alpha/beta-hydrolase fold family member from an Ochrobactrum sp. strain, is a novel N-acylhomoserine lactonase.
N-acylhomoserine lactones (AHLs) are signaling molecules in many quorum-sensing (QS) systems that regulate interactions between various pathogenic bacteria and their hosts. Quorum quenching by the enzymatic inactivation of AHLs holds great promise in preventing and treating infections, and several such enzymes have been reported. In this study, we report the characterization of a novel AHL-degrading protein from the soil bacterium Ochrobactrum sp. strain T63. This protein, termed AidH, shares no similarity with any of the known AHL degradases but is highly homologous with a hydrolytic enzyme from Ochrobactrum anthropi ATCC 49188 that contains the alpha/beta-hydrolase fold. By liquid chromatography-mass spectrometry (MS) analysis, we demonstrate that AidH functions as an AHL-lactonase that hydrolyzes the ester bond of the homoserine lactone ring of AHLs. Mutational analyses indicate that the G-X-Nuc-X-G motif or the histidine residue conserved among alpha/beta-hydrolases is critical for the activity of AidH. Furthermore, the AHL-inactivating activity of AidH requires Mn(2+) but not several other tested divalent cations. We also showed that AidH significantly reduces biofilm formation by Pseudomonas fluorescens 2P24 and the pathogenicity of Pectobacterium carotovorum, indicating that this enzyme is able to effectively quench QS-dependent functions in these bacteria by degrading AHLs.
Department of Plant Pathology, China Agricultural University, Beijing 100193, China.
Gui-Ying
GY
Mei
Xiao-Xue
XX
Yan
Ali
A
Turak
Zhao-Qing
ZQ
Luo
Li-Qun
LQ
Zhang
D054742:Acyl-Butyrolactones / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D020134:Catalytic Domain; D002413:Cations, Divalent / Q000378:metabolism; D002853:Chromatography, Liquid; D003067:Coenzymes / Q000378:metabolism; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D008345:Manganese / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D042041:Ochrobactrum / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D016973:Pectobacterium carotovorum / Q000187:drug effects / Q000472:pathogenicity; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000254:growth & development; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012988:Soil Microbiology
D054742:Acyl-Butyrolactones; D001426:Bacterial Proteins; D002413:Cations, Divalent; D003067:Coenzymes; D004269:DNA, Bacterial; D008345:Manganese; D002265:Carboxylic Ester Hydrolases; C432003:N-acyl homoserine lactonase