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Figure 2. In a typical two-component signal transduction system, the transmembrane domain of the histine kinase recognizes a stimulus. Upon recognition, the histidine kinase catalyzes ATP-dependent autophosphorylation of a conserved histidine residue in the dimerization domain. The phosphoryl group is subsequently transferred to a conserved aspartate residue in the regulatory domain of the cognate response regulator. Phosphorylation activates the effector domain of the response regulator. The activated response regulator will then activate or repress transcription of specific target gene(s), promoting a specific response.
