An electrochemical approach to chemically driven proton pumps: The effects of secondary reactions, uncouplers, inhibitors and ionophores

Abstract

The concept of proton transfer in biological membranes in terms of proton-involved chemical reactions (R. Naumann, Bioelectrochem. Bioenerg., 16 (1986) 245) is pursued further. The vectorical character of proton flow is assumed to be caused by oscillations superimposed on a steady state. Oscillations are explained in terms of the theory of metastable states and hysteresis put forward by A. Katchalsky and R. Spangler (Q. Rev. Biophys., 1 (1968) 127). According to this theory, cooperative phenomena connected with permeability changes of membrane proteins are responsible for feedback control between the oscillations of proton flow and the electrostatic potential at the membrane/water interface, Δψ. Following the quasi-stationary state approach, the driving force of proton transfer is, however, taken to be the transmembrane Δ ▪ H + rather than Δψ. Proton flow as a function of Δ ▪ H + is treated in terms of the theory of electrochemical kinetics. Using computer calculations, this treatment is shown to be in qualitative agreement with experimental findings regarding the effects given in the title.