EFFECT OF NA3VO4 AND MEMBRANE-POTENTIAL ON THE STRUCTURE OF SARCOPLASMIC-RETICULUM MEMBRANE

Two-dimensional crystalline arrays of Ca2+-ATPase molecules develop after treatment of sarcoplasmic reticulum vesicles with Na3VO4 in a Ca2+-free medium. The influence of membrane potential upon the rate of crystallization was studied by ion substitution using oxonol VI and 3,3''-diethyl-2,2''-thiadicarbocyanine (Di-S-C2(5)) to monitor inside positive or inside negative membrane potentials, respectively. Positive transmembrane potential accelerates the rate of crystallization of Ca2+-ATPase, while negative potential disrupts preformed Ca2+-ATPase, while negative potential disrupts preformed Ca2+-ATPase crystals, suggesting an influence of transmembrane potential upon the conformation of Ca2+-ATPase.