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Mechanism of competence activation by the ComRS signalling system in streptococci
Article first published online: 4 FEB 2013
© 2013 Blackwell Publishing Ltd
Volume 87, Issue 6, pages 1113–1132, March 2013
How to Cite
Fontaine, L., Goffin, P., Dubout, H., Delplace, B., Baulard, A., Lecat-Guillet, N., Chambellon, E., Gardan, R. and Hols, P. (2013), Mechanism of competence activation by the ComRS signalling system in streptococci. Molecular Microbiology, 87: 1113–1132. doi: 10.1111/mmi.12157
- Issue published online: 11 MAR 2013
- Article first published online: 4 FEB 2013
- Accepted manuscript online: 17 JAN 2013 03:34AM EST
- Manuscript Accepted: 9 JAN 2013
- Belgian Science Policy Office
In many streptococci, competence for natural DNA transformation is regulated by the Rgg-type regulator ComR and the pheromone ComS, which is sensed intracellularly. We compared the ComRS systems of four model streptococcal species using in vitro and in silico approaches, to determine the mechanism of the ComRS-dependent regulation of competence. In all systems investigated, ComR was shown to be the proximal transcriptional activator of the expression of key competence genes. Efficient binding of ComR to DNA is strictly dependent on the presence of the pheromone (C-terminal ComS octapeptide), in contrast with other streptococcal Rgg-type regulators. The 20 bp palindromic ComR-box is the minimal genetic requirement for binding of ComR, and its sequence directly determines the expression level of genes under its control. Despite the apparent species-specific specialization of the ComR–ComS interaction, mutagenesis of ComS residues from Streptococcus thermophilus highlighted an unexpected permissiveness with respect to its biological activity. In agreement, heterologous ComS, and even primary sequence-unrelated, casein-derived octapeptides, were able to induce competence development in S. thermophilus. The lack of stringency of ComS sequence suggests that competence of a specific Streptococcus species may be modulated by other streptococci or by non-specific nutritive oligopeptides present in its environment.