Rabbit skeletal muscle F-actin can be stable at low ionic strength, provided trace amounts of Ca2+ are absent.
Addition of low concentrations (0.2--2.0 mM) of EGTA to rabbit skeletal muscle G-actin in the presence of ATP caused increase in viscosity. The effect is probably due to chelation of Ca2+. EGTA-polymerized actin was sedimented in the ultracentrifuge as a pellet which could be depolymerized in the presence of Ca2+ and then repolymerized. Electron microscopy indicated that formation of filamentous actin which appears to be somewhat more flexible than F-actin obtained by polymerization with KCl. The EGTA-polymerized actin was dissociated by DNAase I faster than KCl-polymerized actin. F-Actin can thus be stable also in very low ionic strength media if Ca2+ is removed whereas for G-actin to be the only form of the protein in such media, micromolar concentrations of Ca2+ must be present.
D000199:Actins / Q000032:analysis*; D000818:Animals; D001704:Biopolymers; D002118:Calcium; D004355:Drug Stability; D004533:Egtazic Acid; D009132:Muscles / Q000032:analysis*; D009994:Osmolar Concentration; D011189:Potassium Chloride; D011817:Rabbits; D014783:Viscosity
D000199:Actins; D001704:Biopolymers; D004533:Egtazic Acid; D011189:Potassium Chloride; D002118:Calcium