At low cell densities, the sensor kinases LuxQ and LuxN autophosphorylate, passing the phosphate signal via LuxU, to LuxO. In its phosphorylated state, LuxO activates the transcription of a repressor of the luxCDABE genes. At high cell densities, the two autoinducer molecules accumulate and interact with the sensors LuxP and LuxN. This causes them to dephosphorylate LuxO (via LuxU) preventing it from activating the expression of the repressor protein. This allows the protein LuxR to activate transcription of the luxCDABE genes.

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