Possible origin of gating current in nerve membrane.

The present information about gating current observed in squid giant axons points towards the distinct possibility of the current arising from the Debye relaxation of the carboxyl groups in the side chains of the globular proteins enclosing the ionic channels. These carboxyl groups form dipole chains stretching across the membrane. A dipole model is constructed to study the relaxation process under the assumption that the relaxation time tau of the dipoles is modified by dipole-dipole interaction. This model explains qualitatively some of the features of the asymmetric gating current, but is not indicative of any specific mechanism leading to the opening of the gates in the ionic channels. We speculate that the conformational change in the protein globules as a result of dipole reorientation would be the key to the mystery.