indirectly_positively_regulates MexAB-OprM protein(s) and two-component regulatory system modulating antibiotic efflux ArmR ARO:3004056 antibiotic_resistance ArmR ArmR, a 53-amino-acid antirepressor, allosterically inhibits MexR dimer-DNA binding by occupying a hydrophobic binding cavity within the center of the MexR dimer. ArmR up-regulation and MexR-ArmR complex formation have previously been shown to upregulate MexAB-OprM.