Control of natural transformation in salivarius Streptococci through specific degradation of σX by the MecA-ClpCP protease complex.
(2014) Journal of Bacteriology — Vol. 196, n° 15, p. 2807-2816 (2014)
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- Competence for natural DNA transformation is a tightly controlled developmental process in streptococci. In mutans and salivarius species, the abundance of the central competence regulator σ(X) is regulated at two levels: transcriptional, by the ComRS signaling system via the σ(X)/ComX/SigX-inducing peptide (XIP), and posttranscriptional, by the adaptor protein MecA and its associated Clp ATPase, ClpC. In this study, we further investigated the mechanism and function of the MecA-ClpC control system in the salivarius species Streptococcus thermophilus. Using in vitro approaches, we showed that MecA specifically interacts with both σ(X) and ClpC, suggesting the formation of a ternary σ(X)-MecA-ClpC complex. Moreover, we demonstrated that MecA ultimately targets σ(X) for its degradation by the ClpCP protease in an ATP-dependent manner. We also identify a short sequence (18 amino acids) in the N-terminal domain of σ(X) as essential for the interaction with MecA and subsequent σ(X) degradation. Finally, increased transformability of a MecA-deficient strain in the presence of subinducing XIP concentrations suggests that the MecA-ClpCP proteolytic complex acts as an additional locking device to prevent competence under inappropriate conditions. A model of the interplay between ComRS and MecA-ClpCP in the control of σ(X) activity is proposed.
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Wahl, A., Servais, F., Drucbert, A.-S., Foulon, C., Fontaine, L., & Hols, P. (2014). Control of natural transformation in salivarius Streptococci through specific degradation of σX by the MecA-ClpCP protease complex. Journal of Bacteriology, 196(15), 2807-2816. https://doi.org/10.1128/JB.01758-14 (Original work published 2014)