Properties of the stochastic energization-relaxation channel model for vectorial ion transport

A model for the primary active transport by an ion pump protein is proposed . The model, the "energization-relaxation channel model," describes an ion pump as a multiion channel that undergoes stochastic transitions between tw o conformational states by external energy supply. When the potential profi le along ion transport pathway is asymmetrical, a net ion flux is induced b y the transitions. In this model, the coupling of the conformational change and ion transport is stochastic and loose. The model qualitatively reprodu ces known properties of active transport such as the effect of ion concentr ation gradient and membrane potential on the rate of transport and the inhi bition of ion transport at high ion concentration. We further examined the effect of various parameters on the ion transport properties of this model. The efficiency of the coupling was almost 100% under some conditions.