Membrane potential changes alter the conformation of Ca2+-ATPase molecules, regulating ATPase-ATPase interactions which may affect Ca2+ transport activity in vivo.
Membrane potential effects on Ca2+-ATPase remain preclinical; leaves open any role in cardiac Ca2+ transport in vivo.
Na3VO4 promotes the crystallization of Ca2+-ATPase in sarcoplasmic reticulum vesicles. The rate of vanadate-induced crystallization is dramatically increased by inside positive membrane potential generated through ion substitution. Negative potential caused the transient disruption of preformed Ca2+-ATPase crystals, followed by slower reappearance of the lattice after the potential was dissipated. We propose that positive transmembrane potential alters the conformation of the Ca2+-ATPase molecules in a manner that favors ATPase-ATPase interactions, while negative potential would have the opposite effect. Changes in enzyme conformation caused by potential changes during the contraction-relaxation cycle could regulate ATPase interactions in a similar manner in vivo, with effects upon the Ca2+ transport activity and permeability of the sarcoplasmic reticulum.
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A. Martonosi (1983) studied this question.
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