MD recognition by MDR gene regulators.

Multidrug resistance (MDR) mechanisms provide responses that sense and extrude arrays of diverse drugs from cellular environments. To do this, MDR functions rely on two linked features--multidrug recognition (MD) and allosteric linkages to drug binding. Crystal structures of drug-bound BmrR and QacR complexes offered the first insights into the details of drug recognition and the canonical view of MD recognition. Recent structural reports provide further support for the canonical theme as well as variations thereof. Multiple drug-bound TtgR and BmrR structures facilitate proposals of binding models, which agree with promiscuous binding and drug-binding profiles. Significantly, the canonical view may be a useful framework to guide future structural interpretations and model proposals. This will be important as alternative depictions of MD recognition become available through more structure determinations.