title: A protein modulator of erythrocyte membrane (Ca2+ + Mg2+)-ATPase inhibitor protein.
abstract: A protein modulator of erythrocyte membrane (Ca2+ + Mg2+)-ATPase inhibitor protein was purified to apparent homogeneity from pig membrane-free hemolysate by a combination of carboxymethyl-Sephadex chromatography, gel filtration, chromatofocusing (pH 7-4) and subsequent removal of trace inhibitor protein by salt treatment. Gel filtration gave a molecular weight of 57500 for the purified protein modulator, while SDS-polyacrylamide gel electrophoresis of dithiothreitol-treated modulator revealed one single band with a molecular weight of 29000. Isoelectric focusing of the dithiothreitol-treated protein revealed one band (isoelectric pH 4.85), while untreated modulator gave an extra band (isoelectric pH 4.96). It contains no methionine and has an acidic amino acid content 73% higher than that of its basic residues. Freshly prepared or dithiothreitol-treated modulator suppressed both pig and human erythrocyte (Ca2+ + Mg2+)-ATPase inhibitor protein activity, but did not affect ATPase and calmodulin activities. Modulator-coupled Affi-Gel 15 could be employed for purification of the protein inhibitor.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000097:blood; D002846:Chromatography, Affinity; D004910:Erythrocyte Membrane / Q000201:enzymology*; D008970:Molecular Weight; D011506:Proteins / Q000302:isolation & purification*; D013552:Swine; D000097795:ATPase Inhibitory Protein
chemical_list: D000596:Amino Acids; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D011506:Proteins; D000097795:ATPase Inhibitory Protein