The regulation of ATPase-ATPase interactions in sarcoplasmic reticulum membrane. II. The influence of membrane potential.
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.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D003460:Crystallization; D008564:Membrane Potentials; D008854:Microscopy, Electron; D009132:Muscles / Q000201:enzymology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000502:physiology; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D014638:Vanadates; D000252:Calcium-Transporting ATPases