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Implication du PTS dans la régulation de PrfA, activateur transcriptionnel des gènes de virulence de Listeria monocytogenes

Abstract : The activity of the Listeria monocytogenes transcription activator PrfA, which is required for the expression of several virulence genes, including the hemolysin-encoding hly, is inhibited by the presence of glucose, fructose and other rapidly metabolizable carbon sources. This inhibition is not mediated via the main carbon catabolite repression mechanism operative in Gram-positive bacteria, since inactivation of the catabolite control protein A (CcpA) did not prevent repression of virulence genes by the above sugars. We used a Bacillus subtilis strain (BUG1199) containing the prfA gene under control of an IPTG-inducible promoter and the lacZ reporter gene fused to the PrfA-activated L. monocytogens hly promoter to test whether the catabolite co-repressor P-Ser-HPr might be involved in PrfA regulation. Indeed, accumulation of P-Ser-HPr in an hprK mutant (hprKV267F) producing HPr kinase/phosphorylase (HprK/P) with normal kinase, but almost no phosphorylase activity strongly inhibited transcription activation by PrfA even in the absence of a repressing sugar. In response to the concentration of certain metabolites, the bifunctional HprK/P either phosphorylates HPr at Ser-46 (kinase function) or dephosphorylates P-Ser-HPr (phosphorylase function). Preventing the formation of P-Ser-HPr in the hprKV267F mutant by replacing Ser-46 in HPr with an alanine restored PrfA activity. In contrast, inactivation of crh, which encodes a HPr homologue that also becomes phosphorylated at Ser-46, did not enhance PrfA activity. PrfA in the hprKV267F mutant also remained inactive when the ccpA gene was mutated. In fact, disruption of ccpA in the hprK wild-type strain BUG1199 also led to the inactivation of PrfA, which is in agreement with previous findings that ccpA mutants contain large amounts of P-Ser-HPr similar to the hprKV267F mutant. It therefore seems that elevated concentrations of P-Ser-HPr due either to growth on rapidly metabolisable carbon sources or to specific mutations directly or indirectly inhibit PrfA activity. To carry out its catalytic function in sugar transport, HPr of the phosphotransferase system (PTS) is also phosphorylated by phosphoenolpyruvate and enzyme I at His-15. However, P-Ser-HPr is only very slowly phosphorylated by enzyme I, which probably accounts for PrfA inhibition. In agreement with this concept, disruption of the enzyme I- or HPr-encoding genes also strongly inhibited PrfA activity. PrfA activity therefore seems to depend on a fully functional PTS phosphorylation cascade.
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https://tel.archives-ouvertes.fr/tel-00132340
Contributor : Jean-Marie Beckerich <>
Submitted on : Wednesday, February 21, 2007 - 3:32:50 PM
Last modification on : Friday, October 23, 2020 - 4:40:25 PM
Long-term archiving on: : Friday, September 21, 2012 - 11:36:03 AM

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  • HAL Id : tel-00132340, version 1
  • PRODINRA : 251905

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Citation

Rana Herro. Implication du PTS dans la régulation de PrfA, activateur transcriptionnel des gènes de virulence de Listeria monocytogenes. Biologie cellulaire. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00132340⟩

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