The lrp gene and its role in type I fimbriation in Citrobacter rodentium.
Citrobacter rodentium is a murine pathogen that is now widely used as an in vivo model for gastrointestinal infections due to its similarities with human enteropathogens, such as the possession of a locus for enterocyte effacement (the LEE island). We studied the lrp gene of C. rodentium and found that it encodes a product highly similar to members of the Lrp (leucine-responsive regulatory protein) family of transcriptional regulators, able to recognize leucine as an effector and to repress the expression of its own structural gene. In enterobacteria, Lrp is a global regulator of gene expression, as it controls a large variety of genes, including those coding for cell appendages and other potential virulence factors. Based on the well-established role of Lrp on the expression of pilus genes in Escherichia coli, we also studied the role of Lrp in controlling the formation of the type I pilus in C. rodentium. Type I pili, produced by the fim system, are virulence factors of uropathogens, involved in mediating bacterial adhesion to bladder epithelial cells. Yeast agglutination assays showed that Lrp is needed for type I pilus formation and real-time PCR experiments indicated that Lrp has a strong leucine-mediated effect on the expression of the fimAICDFGH operon. Mutant studies indicated that this positive action is exerted mainly through a positive control of Lrp on the phase variation mechanism that regulates fimAICDFGH expression. A quantitative analysis of its expression suggested that this operon may also be negatively regulated at the level of transcription.
Cordone
Angela
A
Dipartimento di Biologia Strutturale e Funzionale, Università Federico II, via Cinthia, Complesso Monte S. Angelo, 80126, Naples, Italy.
Mauriello
Emilia M F
EM
Pickard
Derek J
DJ
Dougan
Gordon
G
De Felice
Maurilio
M
Ricca
Ezio
E
D044082:Citrobacter rodentium / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D051756:Leucine-Responsive Regulatory Protein; D009154:Mutation; D009876:Operon / Q000502:physiology; D010641:Phenotype; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014774:Virulence; D037521:Virulence Factors / Q000502:physiology
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; D014157:Transcription Factors; D037521:Virulence Factors; D051756:Leucine-Responsive Regulatory Protein