title: Mechanism of competence activation by the ComRS signalling system in streptococci.
abstract: 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.
authors: Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, B-1348, Louvain-la-Neuve, Belgium. laetitia.fontaine@uclouvain.be
authors: Laetitia
authors: L
authors: Fontaine
authors: Philippe
authors: P
authors: Goffin
authors: Hélène
authors: H
authors: Dubout
authors: Brigitte
authors: B
authors: Delplace
authors: Alain
authors: A
authors: Baulard
authors: Nathalie
authors: N
authors: Lecat-Guillet
authors: Emilie
authors: E
authors: Chambellon
authors: Rozenn
authors: R
authors: Gardan
authors: Pascal
authors: P
authors: Hols
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D019295:Computational Biology; D061269:DNA Transformation Competence; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D010675:Pheromones / Q000378:metabolism; D011485:Protein Binding; D013291:Streptococcus / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D010675:Pheromones