Fig. 2.
Substrate specificities of MexEF-OprN and MexHI-OpmD from P. aeruginosa. When overproduced, and in the context of the outer membrane permeability barrier, the two pumps have overlapping substrate specificities and provide the same levels of resistance to structurally diverse fluoroquinolones. Their actual substrate specificities are distinct, with MexHI-OpmD selective for phenazines [59]. EtBr, ethidium bromide; PMS, phenazine methosulfate; PCA, phenazine-1-carboxylic acid.