Nonactin

Nonactin is a cyclic ionophore and part of the macrotetrolide antibiotics family. The ionophore is commonly produced by several species of Streptomyces which selectively binds K⁺ and NH₄⁺. Nonactin has been recorded to function by binding a metal ionophore and transporting it across cell membranes for release. The compound can functionally perform this transport due to its conformational flexibility and hydrophobic exterior. The compound forms a natural diastereomer which is required for its antibacterial and binding capacities.

At a concentration of 1x10^-7 M Nonactin uncoupled oxidative phosphorylation and induced ATP hydrolysis. The compound has been observed to specifically inhibit the processing of cytoplasmic precursor proteins destined for the mitochondria. In the presence of Thallus acetate, Nonactin has further stimulated the swelling of rat liver mitochondria than thallus acetate alone. It also has inhibited the effects on P170 glycoprotein-mediated efflux of chemotherapeutic agents in MDR cancer cells. Nonactin has been shown to inhibit the production and gene transcription of IL-5 but not of IL-2 or IL-4. Nonactin has also been used as an ammonium ionophore for ammonium ion determination in a potentiometric electrode for biosensor construction as well as in a fluorescent immuno assay to detect K⁺ ions in pharmaceutical samples.