The ion-conducting properties of Ca2+ ATPase in rabbit skeletal muscle sarcoplasmic reticulum.

Ca2+ ATPase was isolated from rabbit skeletal muscle sarcoplasmic reticulum and used to form structures resembling potential-dependent calcium channels within the membrane lipid bilayer of liposomes. The orientation of these structures in the bilayer was dependent on the conditions used for enzyme incorporation. The results obtained indicate that Ca2+ ATPase may be involved in the passive transport of calcium ions from the sarcoplasmic reticulum which may be regulated by the membrane potential. The membrane potential within the reticulum is probably positive at the moment of calcium ion release.