title: Interaction between cytoplasmic (Ca2+--Mg2+) ATPase activator and the erythrocyte membrane.
abstract: Human red blood cells (RBC) contain a cytoplasmic, nonhemoglobin protein which activates the (Ca2+-Mg2+)ATPase of isolated RBC membranes. Results presented in this paper confirm that activation of (Ca2+-Mg2+)ATPase is associated with binding of the cytoplasmic activator to the membrane. Binding of the cytoplasmic activator is reversible and dependent on ionic strength and Ca2+. Cytoplasmic activator is sensitive to trypsin but is not degraded when intact RBC are exposed to trypsin. Cytoplasmic activator does not modify the (Ca2+-Mg2+)-ATPase of membranes from RBC exposed to activator prior to hemolysis. Thus, the activator is located in the cell and appears to act by binding to the inner membrane surface.
mesh_terms: D000251:Adenosine Triphosphatases / Q000097:blood*; D002021:Buffers / Q000494:pharmacology; D002118:Calcium; D002147:Calmodulin / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008274:Magnesium; D014357:Trypsin / Q000494:pharmacology
chemical_list: D002021:Buffers; D002147:Calmodulin; D014357:Trypsin; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium