title: On the failure of calmodulin to activate Ca2+ pump ATPase of dog red blood cells.
abstract: Ca2+-pump ATPase activities of membranes isolated from human and dog RBCs were compared under a variety of conditions. Specific activity of the dog enzyme was less than that of human. Unlike the human enzyme, the dog Ca2+-pump ATPase was not stimulated by exogenously added calmodulin (CaM) or oleate. The Ca2+ dependence of the dog Ca2+-pump ATPase resembled that of the CaM-activated form of the human enzyme. Cross-linking of Azido-125I-CaM to dog RBC membranes did not label a Ca2+-pump ATPase of molecular weight similar to that found in human RBC membranes. It is suggested that the Ca2+-pump ATPase in isolated dog RBC membranes exists in an activated state, not due to endogenous CaM, but possibly due to partial proteolysis.
authors.forename: J W
authors.initials: JW
authors.lastname: Schmidt
authors.forename: T R
authors.initials: TR
authors.lastname: Hinds
authors.forename: F F
authors.initials: FF
authors.lastname: Vincenzi
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000097:blood; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002147:Calmodulin / Q000494:pharmacology*; D004285:Dogs; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D013045:Species Specificity
chemical_list: D002147:Calmodulin; D000252:Calcium-Transporting ATPases; D002118:Calcium