title: Rat brain has the alpha 3 form of the (Na+,K+)ATPase.
abstract: Multiple forms of the catalytic subunit of the (Na+,K+)ATPase have been identified in rat brain. While two of them (alpha 1 and alpha 2) have been well characterized, the third form (alpha 3) of these catalytic subunits only recently has been described by cDNA cloning; the corresponding polypeptide has not been isolated. In this paper it is shown that rat brain contains the alpha 3 chain. The catalytic subunits of the (Na+, K+)ATPase from rat brain axolemma were purified by SDS-PAGE and subjected to formic acid cleavage. Amino acid sequence analysis of the resulting fragments revealed that axolemma has the alpha 3 form of the catalytic subunit. In addition, alpha 3-specific antiserum was raised in rabbits immunized with a synthetic peptide. Immunoblotting with this antiserum revealed that the alpha 3 form of the (Na+,K+)ATPase is present also in whole brain microsomes. In SDS-PAGE, the mobilities of the three catalytic subunits of brain (Na+, K+)ATPase follow the order alpha 1 greater than alpha 2 greater than alpha 3. Determination of the ouabain-inhibitable ATPase activity indicates that if the alpha 3 form of the (Na+,K+)ATPase is able to hydrolyze ATP, it is present in a form of the enzyme with a high affinity for this cardiac glycoside and is similar to the alpha 2 form in this respect.
authors.affiliation: Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: Y M
authors.initials: YM
authors.lastname: Hsu
authors.forename: G
authors.initials: G
authors.lastname: Guidotti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D007668:Kidney / Q000201:enzymology; D046911:Macromolecular Substances; D008297:Male; D008861:Microsomes / Q000201:enzymology; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology; D009928:Organ Specificity; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase