Calcium binding to rat heart plasma membranes: isolation and purification of a lipoprotein component with a high calcium binding capacity

A calcium binding lipoprotein component of rat heart plasma membrane was isolated, purified, and characterized. The lipoprotein complex had an apparent molecular weight of 71 400. One mole of lipoprotein contained 90 mol of phospholipid and 1 mol of a 12 300 molecular weight protein. The maximum calcium binding capacity was 4.27 mu mol/mg of protein, which corresponded to 52 mol of calcium per mol of lipoprotein complex. Calcium binding was competitively inhibited by a variety of metal ions and experimental antiarrhythmic and anesthetic agents.