HTH-type transcriptional regulator QacR (QacR) (QacR)

HTH-type transcriptional regulator QacR (QacR) is a member of the TetR family of transcriptional repressors, primarily identified in Staphylococcus aureus (UniProt, 2024). It plays a pivotal role in bacterial multidrug resistance by controlling the expression of the QacA efflux pump, which exports a wide variety of toxic cationic lipophilic compounds from the cell (Grkovic et al., 1998). QacR functions by binding as a pair of dimers to the operator region of the qacA gene, thereby inhibiting its transcription under basal conditions (Schumacher et al., 2002). The protein is distinguished by an unusually large and flexible multidrug-binding pocket that can accommodate structurally diverse ligands, including quaternary ammonium disinfectants, antiseptic dyes, and plant alkaloids (Grkovic et al., 2003). When these ligands bind to QacR, they induce a coil-to-helix conformational change that reduces the protein's affinity for DNA, resulting in the derepression of qacA and the subsequent efflux of the inducing agents (Schumacher et al., 2001). As a key regulator of resistance in clinical pathogens like MRSA, QacR is a significant target for the development of antimicrobial adjuvants designed to bypass or inhibit bacterial resistance mechanisms (Tahlan et al., 2009).

Other names

HTH-type transcriptional regulator QacRqacRRepressor of qacAQuaternary ammonium compound-resistance repressor

QacR represses the transcription of the qacA multidrug efflux pump gene by binding to its operator sequence as a pair of dimers; binding of inducing ligands to the QacR multidrug-binding pocket triggers a conformational change that causes the protein to dissociate from DNA, thereby inducing qacA expression (Grkovic et al., 1998; Schumacher et al., 2001).