Signal-sensing triggers the shutdown of HemKR, regulating heme and iron metabolism in the spirochete Leptospira biflexa.

ABSTRACT.- Heme and iron metabolic pathways are highly intertwined, both compounds being essential for key biological processes, yet becoming toxic if overabundant.Their concentrations are exquisitely regulated, including via dedicated two-component systems (TCSs) that sense signals and regulate adaptive responses.HemKR is a TCS present in both saprophytic and pathogenic Leptospira species, involved in the control of heme metabolism.However, the molecular means by which HemKR is switched on/off in a signal-dependent way, are still unknown.Moreover, a comprehensive list of HemKR-regulated ge