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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.
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) is processed and exported by ABC-transporters. When a threshold level is reached, the extracellular peptides (
) bind to a histidine kinase receptor (HK) in the cell membrane, resulting in autophosphorylation of the histidine phosphotransferase domain. The phosphate (P) is transferred to the cognate response regulator (RR), which can then bind to target DNA and alter gene expression.
)produced by the cells diffuse freely through the cell envelope. When a threshold level is reached, the signal molecules bind to and activate the transcriptional activator (TA). The signal-TA complex binds to target DNA and alters gene expression.