In:
BMC Microbiology, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2009-12)
Abstract:
Quorum sensing is a term describing a bacterial communication system mediated by the production and recognition of small signaling molecules. The LuxS enzyme, catalyzing the synthesis of AI-2, is conserved in a wide diversity of bacteria. AI-2 has therefore been suggested as an interspecies quorum sensing signal. To investigate the role of endogenous AI-2 in protein expression of the Gram-negative pathogen Salmonella enterica serovar Typhimurium ( S . Typhimurium), we performed a 2D-DIGE proteomics experiment comparing total protein extract of wildtype S . Typhimurium with that of a luxS mutant, unable to produce AI-2. Results Differential proteome analysis of wildtype S . Typhimurium versus a luxS mutant revealed relatively few changes beyond the known effect on phase 2 flagellin. However, two highly differentially expressed protein spots with similar molecular weight but differing isoelectric point, were identified as LuxS whereas the S . Typhimurium genome contains only one luxS gene. This observation was further explored and we show that the S . Typhimurium LuxS protein can undergo posttranslational modification at a catalytic cysteine residue. Additionally, by constructing LuxS-βla and LuxS-PhoA fusion proteins, we demonstrate that S . Typhimurium LuxS can substitute the cognate signal peptide sequences of β-lactamase and alkaline phosphatase for translocation across the cytoplasmic membrane in S . Typhimurium. This was further confirmed by fractionation of S . Typhimurium protein extracts, followed by Western blot analysis. Conclusion 2D-DIGE analysis of a luxS mutant vs . wildtype Salmonella Typhimurium did not reveal new insights into the role of AI-2/LuxS in Salmonella as only a small amount of proteins were differentially expressed. However, subsequent in depth analysis of the LuxS protein itself revealed two interesting features: posttranslational modification and potential translocation across the cytoplasmic membrane. As the S . Typhimurium LuxS protein does not contain obvious signal motifs, it is speculated that LuxS is a new member of so called moonlighting proteins. These observations might have consequences in future studies on AI-2 quorum signaling in S . Typhimurium.
Type of Medium:
Online Resource
ISSN:
1471-2180
DOI:
10.1186/1471-2180-9-198
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2009
detail.hit.zdb_id:
2041505-9
SSG:
12
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