Lrp acts as both a positive and negative regulator for type 1 Fimbriae production in Salmonella enterica serovar Typhimurium

Chang Ho Baek, Ho Young Kang, Kenneth L. Roland, Roy Curtiss

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Leucine-responsive regulatory protein (Lrp) is known to be an indirect activator of type 1 fimbriae synthesis in Salmonella enterica serovar Typhimurium via direct regulation of FimZ, a direct positive regulator for type 1 fimbriae production. Using RT-PCR, we have shown previously that fimA transcription is dramatically impaired in both lrp-deletion (Δlrp) and constitutive-lrp expression (lrp C) mutant strains. In this work, we used chromosomal P fimA-lacZ fusions and yeast agglutination assays to confirm and extend our previous results. Direct binding of Lrp to P fimA was shown by an electrophoretic mobility shift assay (EMSA) and DNA footprinting assay. Site-directed mutagenesis revealed that the Lrp-binding motifs in P fimA play a role in both activation and repression of type 1 fimbriae production. Overproduction of Lrp also abrogates fimZ expression. EMSA data showed that Lrp and FimZ proteins independently bind to P fimA without competitive exclusion. In addition, both Lrp and FimZ binding to P fimA caused a hyper retardation (supershift) of the DNA-protein complex compared to the shift when each protein was present alone. Nutrition-dependent cellular Lrp levels closely correlated with the amount of type 1 fimbriae production. These observations suggest that Lrp plays important roles in type 1 fimbriation by acting as both a positive and negative regulator and its effect depends, at least in part, on the cellular concentration of Lrp in response to the nutritional environment.

Original languageEnglish (US)
Article numbere26896
JournalPloS one
Volume6
Issue number10
DOIs
StatePublished - Nov 2 2011

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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