67 k calcimedin (67 kDa) is distinct from p67 calelectrin and lymphocyte 68 kDa Ca2+-binding protein

The 67 k calcimedin is a Ca2+-binding protein present in both muscle cells and peritoneal macrophages. Many tissues, including lymphoid tissues, liver and lymphocytes, have been shown to contain Ca2+-binding proteins of similar molecular size, such as the p67(67 kDa) calelectrin or the 68 kDa lymphocyte protein. We have tested affinity-purified antibodies raised to the smooth-muscle 67 k calcimedin in these several tissues and here report that the 67 k calcimedin is not detectable in liver, thymus, spleen or thymic lymphocytes. These findings support recent biochemical evidence, discussed here, suggesting that the 67 k calcimedin is a protein different from calelectrin and the 68 kDa lymphocyte protein. The more limited tissue distribution of the 67 k calcimedin, which includes muscle and macrophages, suggests that the 67 k calcimedin may function in Ca2+-mediated events special to these cell types. The affinity-purified antibodies to the 67 k calcimedin will be useful in obtaining information concerning the special roles of this Ca2+-binding protein in these cells.