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Mechanism of competence activation by the ComRS signalling system in streptococci
Author(s) -
Fontaine Laetitia,
Goffin Philippe,
Dubout Hélène,
Delplace Brigitte,
Baulard Alain,
LecatGuillet Nathalie,
Chambellon Emilie,
Gardan Rozenn,
Hols Pascal
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12157
Subject(s) - biology , gene , genetics , activator (genetics) , in silico , mutant , microbiology and biotechnology
Summary 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 S treptococcus 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 S treptococcus species may be modulated by other streptococci or by non‐specific nutritive oligopeptides present in its environment.

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