Research ArticleMicrobiology

Activation of master virulence regulator PhoP in acidic pH requires the Salmonella-specific protein UgtL

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Sci. Signal.  29 Aug 2017:
Vol. 10, Issue 494, eaan6284
DOI: 10.1126/scisignal.aan6284

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A helping hand for acid sensing

Activation of the PhoP/PhoQ two-component system of Salmonella enterica promotes the expression of virulence factors. Stimuli, such as acidic pH, low Mg2+, or antimicrobial peptides, stimulate the sensor kinase PhoQ to undergo autophosphorylation, which enables PhoQ to phosphorylate the response regulator PhoP. Phosphorylated PhoP then binds to and stimulates the transcription of target genes. Choi and Groisman found that the Salmonella-specific protein UgtL enhanced acid-induced activation of the PhoP/PhoQ system but had no effect on the activation of this system by low Mg2+ or antimicrobial peptides. UgtL promoted the phosphorylation of PhoP by enhancing the autophosphorylation of PhoQ, but it had no effects on phosphotransfer from PhoQ to PhoP or dephosphorylation of PhoP by PhoQ. Compared to wild-type Salmonella, ugtL mutants exhibited reduced virulence in mice. Thus, this horizontally acquired factor has become an important determinant of Salmonella virulence.