Figure 2.

The basic mechanisms of a two-component signaling system. The sensor HK senses the environmental signal using the sensing domain that is connected to the signal transduction domain, a cytoplasmic sensor domain, an ATP catalytic domain, and a dimerization histidine phosphotransfer domain (DHp). The conserved histidine residue of HK transfers the phosphate to the conserved aspartate residue of the receiver domain of its RR. The effector domain of the phosphorylated RR binds to its target and regulates gene expression.