FIG 1.

c-di-AMP signaling in Streptococcus pneumoniae. CdaR directly interacts with the diadenylate cyclase CdaA and regulates its activity (7). The red arrows indicate the possibilities of how the Trk family protein CabP modulates the cellular c-di-AMP level. The CabP-dependent control of c-di-AMP synthesis or degradation might also depend on additional factors, as indicated by the yellow circle. Moreover, CabP could control the activity of an unknown additional potassium transporter, and the changes in cellular potassium concentration could then affect the c-di-AMP levels.