Nigericin

Nigericin is a polyether antibiotic and ionophore produced by certain Streptomyces species. It functions as a potassium/proton (K+/H+) antiporter that couples the transport of K+ and H+ across biological membranes. In the presence of potassium, nigericin binds H+ and K+ to form a neutral complex that shuttles through the lipid bilayer, dissipating transmembrane gradients. As a result it collapses proton motive force and can alter membrane potential, depending on experimental conditions. Nigericin activity is selective for monovalent cations, with a preference for K+ over Na+ in many systems.

In laboratory settings, nigericin is used as a mechanistic tool to collapse pH gradients across membranes. It is frequently employed in studies of mitochondrial energetics, to dissipate ΔpH and to study the relationship between proton gradients and ATP synthesis, respiration, and ion transport. It can also be used to calibrate intracellular pH measurements in cells and vesicles. Because of its broad bioactivity and toxicity, nigericin is not used clinically.

Nigericin belongs to the nigericin family of polyether antibiotics, characterized by a cage-like, multi-ring structure that forms ion-binding cavities. It is produced by Streptomyces hygroscopicus subsp. niger, among other Streptomyces strains, during secondary metabolism. Research uses focus on its ionophoric properties and incorporation into liposome-based assays and bioenergetic experiments.