Multidrug-binding transcriptional repressor QacR (QacR)

The Multidrug-binding transcriptional repressor QacR is a member of the TetR family of transcriptional regulators, primarily found in Staphylococcus aureus. It plays a critical role in bacterial multidrug resistance by regulating the expression of the qacA gene, which encodes a major multidrug efflux pump (Schumacher et al., 2001). QacR is distinguished by its ability to recognize and bind an exceptionally broad range of structurally diverse cationic lipophilic compounds, including common antiseptics like chlorhexidine and dyes like crystal violet (Grkovic et al., 2003). Under normal conditions, QacR binds as a pair of dimers to the IR1 operator DNA, sterically hindering RNA polymerase and repressing transcription. When a ligand binds to the expansive, multisite binding pocket of QacR, it triggers a coil-to-helix conformational change that causes the protein to dissociate from the DNA, thereby inducing the expression of the QacA pump and facilitating the efflux of toxic agents (Schumacher et al., 2002). This mechanism makes QacR a significant target for research aimed at overcoming antibiotic resistance in pathogenic bacteria.

Other names

HTH-type transcriptional regulator QacRQacR repressorStaphylococcus aureus QacRMultidrug resistance protein R

QacR acts as a transcriptional repressor that binds to the operator of the qacA gene; ligand binding induces a conformational change that releases the repressor from DNA, allowing transcription of the multidrug efflux pump.