Purification of a protein inhibitor of erythrocyte plasma membrane Ca(2+)-ATPase by Ca(2+)-ATPase-sepharose affinity chromatography.

A protein inhibitor of erythrocyte plasma membrane Ca(2+)-ATPase was purified to homogeneity using a Ca(2+)-ATPase-Sepharose affinity column. Inhibitor isolated by anion exchange chromatography was loaded onto the affinity column in the presence of Ca2+ and the purified inhibitor was eluted with EGTA. The estimated yield was 0.1-0.2 mg protein inhibitor/1. red cells. SDS-polyacrylamide gel electrophoresis of freshly purified inhibitor revealed one single silver stained band with an apparent molecular mass of 50-51 kD.