Investigating Post-Translational Regulation of the SloR Metalloregulator in Streptococcus mutans

Streptococcus mutans is a member of the human oral microbiota and the primary causative agent of dental caries. To develop a treatment that can curtail S. mutans’ ill effects on oral health, we study a 25kDa SloR... [ view full abstract ]

Streptococcus mutans is a member of the human oral microbiota and the primary causative agent of dental caries. To develop a treatment that can curtail S. mutans’ ill effects on oral health, we study a 25kDa SloR metalloregulatory protein which binds to DNA as a global regulator of S. mutans virulence genes.  Previous work in our laboratory revealed increased transcription of oxidative stress genes in a S. mutans SloR-deficient mutant, and direct SloR binding to the S. mutans spxA promoter which enhances transcription of these and other oxidative stress genes.  Immunoblotting with the S. mutans ClpX, ClpE, and ClpP insertion-deletion mutants revealed SloR accumulation.  We propose that SloR, as a modulator of the oxidative stress response, may be subject to proteolytic degradation by the Clp protease complex when S. mutans is challenged with oxidative stress. Immunoblotting was used to investigate the relationship between the SloR and Clp proteins by monitoring their abundance in the presence of 0.5mM H₂O₂ for up to 60 minutes.  Western blots with UA159 whole cell lysates revealed a decrease in SloR after 15 minutes of H₂O₂ exposure, and an increase in ClpE after 30 minutes of exposure. A bacterial two hybrid system was used to test for a direct SloR-ClpE interaction.  In sum, the results of this study can elucidate how S. mutans controls SloR post-translationally, and foster strategies for targeting the oxidative stress response to attenuate S. mutans-induced cariogenesis.