The functional unit of Na,K-ATPase is a monomeric alphabeta protomer.
The ouabain-resistant and ouabain-sensitive alpha-subunit cRNAs in various molar ratios were injected into Xenopus oocytes together with cRNA for the beta-subunit. The ouabain-resistant ATPase activity, as well as ouabain-resistant Rb+ uptake, of the injected oocytes increased linearly with increasing the amount of cRNA for the ouabain-resistant alpha-subunit. When a functionless mutant was used instead of the ouabain-sensitive alpha-subunit, similar results were obtained in ATPase activity and Rb+ uptake. These results indicate that a monomeric alphabeta protomer is a functional unit of membrane-bound Na,K-ATPase, even if the enzyme exists structurally as a diprotomer or higher oligomers in membranes.
Takeda
K
K
Department of Biology, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan.
Kawamura
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004274:DNA, Recombinant; D004305:Dose-Response Relationship, Drug; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D021122:Protein Subunits; D018075:RNA, Complementary / Q000008:administration & dosage / Q000235:genetics; D012413:Rubidium / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
D004274:DNA, Recombinant; D021122:Protein Subunits; D018075:RNA, Complementary; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium