Interaction of adenylate cyclase CyaC with regulators Smc01817 and Clr ofSinorhizobium meliloti: cAMP as an ON/OFF trigger in sensor-regulator complexes?

Abstract

AbstractThe symbiotic bacteriumSinorhizobium meliloticontains a large number of adenylate cyclases (AC) for the control of different life styles. ACs produce cyclic AMP (cAMP) as a secondary messenger. Earlier, the redox responsive membrane-intrinsic AC CyaC has been shown to produce a trimeric signalling complex CyaC×CycR×cAMP-Clr. Here, use of the bacterial two-hybrid system BACTH showed that the LysR-type transcriptional regulator Smc01817 interactsin vivowith CyaC and the general cAMP-regulator Clr, suggesting the formation of a sensor-regulator complex CyaC×Smc01817×cAMP-Clr. Therefore, formation of sensor-regulator complexes from ACs and transcriptional regulators seems to be a means inS. melilotito setup specific signalling routes in a background with a large number of signalling routes applying the same signalling molecule (cAMP). Use of caged cAMP allows to address a specific signalling route and set of regulators, which is at variance with the classical role of cAMP as a diffusing secondary messenger.