2-Aminoperimidine, a specific inhibitor of bacterial NhaA Na ⁺/H ⁺ antiporters

The diuretic drug amiloride and its numerous derivatives are competitive inhibitors of mammalian Na ⁺/H ⁺ antiporters and other eukaryotic antiporters. Most prokaryotic antiporters, including the major NhaA family of enterobacteria, are resistant to these compounds. We show that 2-aminoperimidine (AP), a guanidine-containing naphthalene derivative with some similarity to amiloride, acts as a specific inhibitor of NhaA from Escherichia coli. Similar concentrations (IC ₅₀ of 0.9 μM) inhibit the proton motive force dependent Na ⁺(Li ⁺)/H ⁺ exchange reaction in inside-out sub-bacterial vesicles (at 10 mM NaCl, pH 8) as well as the initial rate of ²²Na ⁺/Na ⁺ exchange mediated by pure NhaA in proteoliposomes. The inhibitor is specific to NhaA type antiporters, so AP is a new tool to study the mechanism and roles of NhaA antiporters of enterobacteria as well as the molecular basis of inhibition by an amiloride-like compound.