Histidine kinases and response regulator proteins in two-component signaling systems

Phosphotransfer-mediated signaling pathways allow cells to sense and respon d to environmental stimuli. Autophosphorylating histidine protein kinases p rovide phosphoryl groups for response regulator proteins which, in turn, fu nction as molecular switches that control diverse effector activities. Stru ctural studies of proteins involved in two-component signaling systems have revealed a modular architecture with versatile conserved domains that are readily adapted to the specific needs of individual systems.