The kinetics of monazomycin-induced voltage-dependent conductance. I. Proof of the validity of an empirical rate equation.

Abstract

Monazomycin (a positively-charged, polyene-like antibiotic) induces a strongly voltage-dependent conductance in thin lipid membranes when added to one of the bathing solutions. The kinetics of conductance changes after a step of membrane potential are only superficially similar to the kinetics of the K+ gating system of squid giant axons, in that the beginning of conductance increases are growth functions of the time, as opposed to power functions of the time. The rate constant (reciprocal of the time constant) of the growth varies with the .apprx. 2.6 power of the monazomycin concentration. The rate constant also varies exponentially with membrane potential such than an e-fold change is associated with a 10-11 mV change of membrane potential. Solutions of a simple differential equation are able to reproduce the actual conductance changes almost exactly. The differential equation is derived from a molecular model and the theoretical equation obtained is used to investigate the gating current of this system and to predict an interesting form of memory.