ION CHANNEL ENZYME IN AN OSCILLATING ELECTRIC-FIELD

To explain the electrical activation of several membrane ATPases, an e lectroconformational coupling (ECC) model has previously been proposed . The model explained many features of experimental data but failed to reproduce a window of the field intensity for the stimulated activity . It is shown here that if the affinities of the ion for the two confo rmational states of the transporter (one with binding site on the left side and the other on the right side of the membrane) are dependent o n the electric field, the field-dependent transport can exhibit the ob served window. The transporter may be described as a channel enzyme wh ich opens to one side of the membrane at a time. It retains the energy -transducing ability of the earlier ECC models. Analysis of the channe l enzyme in terms of the Michaelis-Menten kinetics has been done. The model reproduced the amplitude window for the electric field-induced c ation pumping by (Na,K)-ATPase.