# Two-Component Regulatory System --- The **two-component regulatory system** is a system [[gene regulation|genetic regulatory]] system that uses [[unicellular cell signaling|signaling]] to allow [[bacteria]] to respond to different external environments. ## Process The two components of the two-component system are the "sensor" that lives in the membrane, and a "response regulator" inside the cell. When the sensor binds to the [[signaling molecule]] in the environment (which is usually a molecule sent by [[quorum sensing|another bacteria]]), then the sensor changes it's shape. When it does that, am [[adenosine triphosphate]] binding site opens up, and ATP phosphorylates the sensor. Now the response regulator goes over and takes that phosphate, brings it to the DNA, and uses that phosphate to either turn on or off a gene, depending. ___