Affiliation:
1. Instituto Gulbenkian de Ciência, 2781-901 Oeiras, Portugal
2. Instituto de Tecnologia Química e Biológica, 2781-901 Oeiras, Portugal
3. Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, Pennsylvania 19081
Abstract
ABSTRACT
Although a variety of bacterial species have been reported to use the interspecies communication signal autoinducer-2 (AI-2) to regulate multiple behaviors, the molecular mechanisms of AI-2 recognition and signal transduction remain poorly understood. To date, two types of AI-2 receptors have been identified: LuxP, present in
Vibrio
spp., and LsrB, first identified in
Salmonella enterica
serovar Typhimurium. In
S.
Typhimurium, LsrB is the ligand binding protein of a transport system that enables the internalization of AI-2. Here, using both sequence analysis and structure prediction, we establish a set of criteria for identifying functional AI-2 receptors. We test our predictions experimentally, assaying key species for their abilities to import AI-2 in vivo, and test their LsrB orthologs for AI-2 binding in vitro. Using these experimental approaches, we were able to identify AI-2 receptors in organisms belonging to phylogenetically distinct families such as the
Enterobacteriaceae
,
Rhizobiaceae
, and
Bacillaceae
. Phylogenetic analysis of LsrB orthologs indicates that this pattern could result from one single origin of the functional LsrB gene in a gammaproteobacterium, suggesting possible posterior independent events of lateral gene transfer to the
Alphaproteobacteria
and
Firmicutes
. Finally, we used mutagenesis to show that two AI-2-interacting residues are essential for the AI-2 binding ability. These two residues are conserved in the binding sites of all the functional AI-2 binding proteins but not in the non-AI-2-binding orthologs. Together, these results strongly support our ability to identify functional LsrB-type AI-2 receptors, an important step in investigations of this interspecies signal.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
80 articles.
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