Genetic analysis of uxuR and exuR genes: evidence for ExuR and UxuR monomer repressors interactions

Abstract

The uxuAB operon is under the dual control of uxuR- and exuR-encoded repressors whereas the exu regulon genes are regulated by the sole ExuR repressor. Mutations affecting the two exuR and uxuR regulatory genes were selected to investigate the relationship between the two repressors. The isolation of exuR and uxuR negative dominant mutations on a multicopy plasmid indicated that the active form of the two repressors was multimeric. The introduction of a uxuR negative dominant allele into a wild-type strain resulted in a significant increase in exu gene expression. This unexpected effect may have been the consequence of the formation of hybrid repressor molecules. This protein must be composed of native ExuR+ subunits aggregated with altered UxuR subunits. The same interference was observed for the exuR negative dominant allele on uxu gene derepression. The hypothesis given here implies that the two regions of the ExuR and UxuR repressors involved in the subunit aggregation present enough homologies to allow the formation of hybrid repressor molecules.

Transcriptional regulation of transport and utilization systems for hexuronides, hexuronates and hexonates in gamma purple bacteria

“…Transport and catabolism of galacturonate and glucuronate are mediated by genes from the UxuR/ExuR regulon. Two transcription factors of this regulon, ExuR and UxuR, are highly similar (49% identity) and capable of cross‐talk (Ritzenthaler et al ., 1985). ExuR regulates expression of the uxaCA , uxaB and exuT operons involved in galacturonate catabolism.…”

Diet-derived galacturonic acid regulates virulence and intestinal colonization in enterohaemorrhagic Escherichia coli and Citrobacter rodentium

“…A high throughput screen for metabolic pathways and transcriptional factors that regulate LEE gene expression identified ExuR as a LEE regulator 13 . ExuR is a member of the GntR family of transcriptional regulators 14 , has been previously characterized as a regulator of sugar acid catabolism in E. coli 15,16 , and is responsive to galacturonic-acid [17][18][19] .…”

Comparative Genomic Analysis of the Hexuronate Metabolism Genes and Their Regulation in Gammaproteobacteria

“…UxuR controls the D-glucuronate metabolism by repressing uxuAB, uidABC, gntP, and its own gene uxuR (3,7,17,(24)(25)(26)(27). ExuR negatively controls most of the genes involved in the metabolism of both D-galacturonate and D-glucuronate, including exuT, uxaCA, uxaB, uxuAB, and exuR (6,22,[24][25][26][27].Understanding the regulation of the uidABC genes may have practical applications. Indeed, inhibiting ␤-glucuronidase produced by the gut flora can prevent the intestinal metabolism of the anticancer drug irinotecan, thereby diminishing life-threatening toxicity and conceivably allowing dose escalation that will enhance the drug's efficacy (33).…”

“…UxuR controls the D-glucuronate metabolism by repressing uxuAB, uidABC, gntP, and its own gene uxuR (3,7,17,(24)(25)(26)(27). ExuR negatively controls most of the genes involved in the metabolism of both D-galacturonate and D-glucuronate, including exuT, uxaCA, uxaB, uxuAB, and exuR (6,22,[24][25][26][27].…”

“…the genes involved in the metabolism of both D-galacturonate and D-glucuronate, including exuT, uxaCA, uxaB, uxuAB, and exuR (6,22,(24)(25)(26)(27).…”