2.B.3 The Nigericin (Nigericin) Family
Nigericin resembles monensin in being a monocarboxylate that catalyzes the electroneutral exchange of an alkali metal for H+ (antiport). However while monensin prefers Na+, nigericin prefers K+. At high K+ concentrations, nigericin can uncouple mitochondrial oxidative phosphorylation, suggesting that it may catalyze K+ uniport.
The generalized reaction (antiport) catalyzed by nigericin is:
K+ (out) + H+ (in) 
K+ (in) + H+ (out)
References associated with 2.B.3 family:
Eisenman, G., G. Szabo, S.G.A. McLaughlin and S.M. Ciani (1973). Molecular basis for the action of macrocyclic carriers on passive ionic translocation across lipid bilayer membranes. Bioenergetics 4: 93-148. 4717529
Harold, F.M., K.H. Altendorf and H. Hirata (1974). Probing membrane transport mechanisms with ionophores. Annals N.Y. Acad. Sci. 235: 149-160. 4527943