Cooperative Effects in Models of Steady-State Transport across Membranes, III. Simulation of Potassium Ion Transport in Nerve

An extremely simple membrane transport model simulates qualitatively the observed flux-potential curves for steady-state potassium ion transport across a nerve (squid) membrane in the special case of high external potassium ion concentration. The transporting units (protein molecules) in the model are assumed to exist in two different conformations, which interact cooperatively. The membrane potential induces a transition between the two conformations by virtue, primarily, of a polarizability difference in the two conformations. Differential proton binding may make an important contribution to this effect.