Autoregulated expression of the gene coding for the leucine-responsive protein, Lrp, a global regulator in Salmonella enterica serovar Typhimurium

Abstract

In this study, the lrp gene encoding the leucine-responsive regulatory protein (Lrp) in Salmonella enterica serovar Typhimurium was found to be negatively autoregulated. Its transcription start site was determined by primer extension analysis, showing that the lrp promoter is located at a different site to that inferred previously from the S. Typhimurium genome sequence. Chromosomal DNA fragments that include the promoter region were bound by purified Lrp protein in vitro, producing up to four distinct protein-DNA complexes. DNase I footprinting identified regions that were protected by the protein in vitro as well as bases that became hypersensitive to DNase I treatment following Lrp binding. A clear pattern of periodic hypersensitivity was detected between positions "130 and +15 that was consistent with wrapping of the DNA around Lrp in a nucleoprotein complex that includes the putative promoter region. Lrp-DNA interaction in this region was fully consistent with the observed repression of lrp transcription by this protein.Leucine was found to modulate Lrp-mediated autorepression by remodelling the Lrp-DNA nucleoprotein complex.

Leucine-Responsive Regulatory Protein (Lrp) Acts as a Virulence Repressor inSalmonella entericaSerovar Typhimurium

“…2). This result is consistent with a previous report for serovar Typhimurium strain SL1344 (66). Based on OD 600 measurements, the lrp(Con) mutant underwent a short lag phase in both LB, although it grew exponentially at about the same rate as the wild-type strain.…”

“…In addition, McFarland and Dorman showed that there was an increase in the amount of lrp transcripts in serovar Typhimurium SL1344 cells grown in MOPS minimal medium compared to cells grown in LB (66). To verify this observation for UK-1 strains, we performed Western blot analysis on cells grown in LB or MOPS minimal medium (Fig.…”

“…It has been reported that Lrp strongly represses its own promoter in E. coli (59). Recently, expression of the lrp gene in serovar Typhimurium SL1344 was found to be autoregulated by direct interaction between Lrp and its promoter, P lrp (66). The Lrp-binding sequences in P lrp include an Lrp-binding motif (5Ј-TGGCATGTTGTACTA-3Ј).…”

“…In addition, although the Salmonella P lrp interacted strongly with Lrp, the Lrp-binding motif in P lrp was an imperfect match with the E. coli consensus sequence. Based on analysis of the known Lrp-binding sites, including the P lrp (66) and P traJ (13) regions in Salmonella and the E. coli consensus sequence, we propose a new Lrp-binding consensus sequence: 5Ј-YRGHW W(G)DTTDWDSYR-3Ј [where Y ϭ C or T; H ϭ not G; W ϭ A or T; D ϭ not C; R ϭ A or G; S ϭ C or G; and (G) ϭ G or none], termed Lrp consensus II, for both E. coli and Salmonella. This consensus motif is of particular interest because it has dyad symmetry, although imperfect, and dyad symmetry has been implicated to be important for specific interaction with Lrp (11).…”

The Global Transcription Factor Lrp Controls Virulence Modulation in Xenorhabdus nematophila

“…In E. coli and Salmonella, lrp expression exhibits negative autoregulation (42)(43)(44). Regulatory feedback can result in multistable gene expression, suggesting a potential mechanism for Lrpdependent X. nematophila VMO switching (6).…”