Lateral electrophoresis and diffusion of Concanavalin A receptors in the membrane of embryonic muscle cell

Abstract

A uniform electric field of 10 V/cm applied across the surface of embryonic toad Xenopus muscle cells results in the asymmetric accumulation of concanavalin A (Con A) receptors toward one side of the cells within 10 min, as visualized by postfield fluorescent Con A labeling. This field produces an extracellular voltage difference of 20 mV across these 20-microns wide cells. The effect is reversible in two respects: (a) Additional exposure of the cell to the same field of opposite polarity for 10 min completely reverses the asymmetric accumulation to the other side of the cell. (b) Relaxation occurs after the removal of the field and results in complete recovery of the uniform distribution in 30 min. Both the accumulation and the recovery movements are independent of cell metabolism, and appear to be electrophoretic and diffusional in nature. The threshold field required to induce a detectable accumulation by the present method is between 1.0 and 1.5 V/cm (corresponding to a voltage difference of 2-3 mV across a 20-microns wide cell). The electrophoretic mobility of the most mobile population of nonliganded Con A receptors is estimated to be about 2 x 10(-3) microns/s per V/cm, while their diffusion coefficient is in the range of 4-7 x 10(-10) cm2/s. Extensive accumulation of the Con A receptors by an electric field results in the formation of immobile aggregates. The Con A receptors appear to consist of a heterogeneous population of membrane components different in their charge properties, mobility, and capability in forming aggregates.