Nonelectrogenic K⁺/H⁺ exchange including proton transfer between a carrier and acid-base groups of phospholipids on membrane surface: Comparison of theoretical and experimental data

A theoretical model of the nigericin-mediated K⁺/H⁺-exchange was proposed taking into account the reaction of the hydrogen-ion transfer between the carrier and the proton binding groups at the membrane surface was proposed. The model included the catalysis of the proton transfer across the interface by some buffer compounds (citrate, MES) observed by Antonenko, Kovbasnjuk and Yaguzhinsky (Biokhimya 1993 v. 58, p. 1037-1044). Calculations showed that in agreement with previous models, the dependence of the flux on the carrier concentration is linear in the absence of the lateral proton exchange. The flux can be increased considerably by the increase in the buffer concentration. The possibility of the lateral proton reactions between the carrier and the surface proton binding sites led to a complex dependence of the flux on the carrier concentration including the saturation curves as well as nonmonotonic curves within some concentration interval. The nigericin-induced hydrogen ion fluxes were measured in the bilayer lipid membranes. Complex nonlinear dependences of the fluxes on the nigericin concentration were observed. It was concluded that the reaction of the lateral proton exchange between nigericin and the surface binding sites was involved in the process of K⁺/H⁺-exchange.