Effects of anions on the Ca2+, H+ and electrical gradients formed by the sarcoplasmic reticulum ATPase in reconstituted proteoliposomes.

The chaotropic character of several ions determines their partition on membrane interfaces with aqueous media as predicted by the Hofmeister series. However, specific characteristics of each individual ion determine its ability to cross the membrane and to influence Ca2+, H+ and electrical gradients produced by the sarcoplasmic reticulum (SR) Ca2+ pump in reconstituted proteoliposomal vesicles. Specific effects of this kind may be relevant to a variety of biological systems, including the excitation-contraction coupling of muscle fibers in which SR plays a prominent role.