The effect of anti-ATPase antibodies upon the Ca++ transport of sarcoplasmic reticulum

Sheep or guinea pig antisera against the purified Ca⁺⁺ transport ATPase of sarcoplasmic reticulum inhibit Ca⁺⁺ transport due to a complement-dependent damage of the membrane, which causes massive leakage of Ca⁺⁺. The Ca⁺⁺-activated ATPase activity is only slightly affected even at ten times higher antibody concentration than that required for inhibition of Ca⁺⁺ transport. Antibodies prepared against the Ca⁺⁺ binding protein (C₁ protein) have no influence upon either ATPase activity or Ca⁺⁺ transport and ferritin-labeled anti-C₁ antibodies do not bind to microsomes.