title: Immunochemical studies on the large polypeptide of electrophorus electroplax (Na+ + K+)-ATPase.
abstract: Antibodies against Lubrol-solubilized Electrophorus electroplax (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) and its 96 000-dalton polypeptide (P96) were raised in rabbits. The P96 antibody does not cross react with the (Na+ + K+)-ATPase from mammalian species and tissues, but it cross reacts with the (Na+ + K+)-ATPase from both Electrophorus electroplax and brain. The combination of enzyme with anti-P96 is found  to inhibit phosphoryl enzyme formation to the same extent that it inhibits enzyme activity. The rate of K+-sensitive dephosphorylation of phosphoryl enzyme appears to be unchanged. These are also found to be true with the antibody against the whole enzyme. Upon tryptic digestion of the enzyme-anti-P96 complex only the large polypeptide of the enzyme is protected. In the case of enzyme-anti-Lubrol-solubilized enzyme complex, both the large and small polypeptides are protected, whereas preimmune sera are without any protecting effect. The data indicate that the phosphoryl acceptor polypeptide and the Lubrol-solubilized electroplax (Na+ + K+)-ATPase from which the polypeptide is derived are phylogenetically distinct from those of the mammalian (Na+ + K+)-ATPases. The selective tryptic resistance of the enzyme-anti-P96 complex indicates that the two polypeptides are spatially well separated, possibly on opposite sides of the membrane.
mesh_terms: D000251:Adenosine Triphosphatases / Q000276:immunology* / Q000378:metabolism; D000818:Animals; D000937:Antigen-Antibody Reactions; D002462:Cell Membrane / Q000201:enzymology; D004557:Electric Organ / Q000201:enzymology*; D004593:Electrophorus; D004789:Enzyme Activation; D005779:Immunodiffusion; D008970:Molecular Weight; D010455:Peptides / Q000276:immunology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D014357:Trypsin
chemical_list: D010455:Peptides; D012964:Sodium; D014357:Trypsin; D000251:Adenosine Triphosphatases; D011188:Potassium