Extraction and localization of a (Ca2+ and Mg2+)-stimulated ATPase in human erythrocyte spectrin.
(1) A water soluble  (Ca2+ plus Mg2+)-activated APTase has been extracted with 0.1 mM EDTA and 0.1 mM ATP from human erythrocyte membranes. (2) The specific activity of the extracted protein is increased 4- to 6-fold in comparison with untreated ghosts. (3) Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [gamma-32P]ATP-labeled erythrocyte membranes shows that the (Ca2+ plus Mg2+)-activated ATPase is located in the "spectrin" region (Mr 220 000-240 000). The radioactivity of these high molecular peptide bands is decreased markedly after the extraction of the ATPase at low ionic strength.
D000251:Adenosine Triphosphatases / Q000097:blood*; D002118:Calcium; D002462:Cell Membrane / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D008274:Magnesium; D008970:Molecular Weight; D012995:Solubility
D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium