Identification of a key amino acid of LuxS involved in AI-2 production in Campylobacter jejuni.
Autoinducer-2 (AI-2) mediated quorum sensing has been associated with the expression of virulence factors in a number of pathogenic organisms and has been demonstrated to play a role in motility and cytolethal distending toxin (cdt) production in Campylobacter jejuni. We have initiated the work to determine the molecular basis of AI-2 synthesis and the biological functions of quorum sensing in C. jejuni. In this work, two naturally occurring variants of C. jejuni 81116 were identified, one producing high-levels of AI-2 while the other is defective in AI-2 synthesis. Sequence analysis revealed a G92D mutation in the luxS gene of the defective variant. Complementation of the AI-2(-) variant with a plasmid encoded copy of the wild-type luxS gene or reversion of the G92D mutation by site-directed mutagenesis fully restored AI-2 production by the variant. These results indicate that the G92D mutation alone is responsible for the loss of AI-2 activity in C. jejuni. Kinetic analyses showed that the G92D LuxS has a ∼100-fold reduced catalytic activity relative to the wild-type enzyme. Findings from this study identify a previously undescribed amino acid that is essential for AI-2 production by LuxS and provide a unique isogenic pair of naturally occurring variants for us to dissect the functions of AI-2 mediated quorum sensing in Campylobacter.
Department of Veterinary Microbiology and Preventative Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America. pplummer@iastate.edu
Paul
P
Plummer
Jinge
J
Zhu
Masato
M
Akiba
Dehua
D
Pei
Qijing
Q
Zhang
D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016123:Campylobacter jejuni / Q000378:metabolism*; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D006714:Homoserine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D007700:Kinetics; D007783:Lactones; D020125:Mutation, Missense
D000596:Amino Acids; D001426:Bacterial Proteins; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D006714:Homoserine; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria
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