Electrogenicity of Na,K- and H,K-ATPase Activity and Presence of a Positively Charged Amino Acid in the Fifth Transmembrane Segment
| Autor: | Käthi Geering, Muriel Burnay, Solange Kharoubi-Hess, Gilles Crambert, Jean Daniel Horisberger |
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| Rok vydání: | 2003 |
| Předmět: |
Models
Molecular Stereochemistry Xenopus ATPase Urinary Bladder Mutant Lysine Gene Expression Transfection Biochemistry Serine Electrochemistry Animals Ouabain Molecular Biology chemistry.chemical_classification biology Cell Membrane Electric Conductivity Cell Biology biology.organism_classification Amino acid Proton-Translocating ATPases Transmembrane domain chemistry Mutagenesis Site-Directed Oocytes Potassium biology.protein Bufo marinus Female Sodium-Potassium-Exchanging ATPase Rubidium Radioisotopes Cation transport |
| Zdroj: | Journal of Biological Chemistry. 278:19237-19244 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m300946200 |
| Popis: | The transport activity of the Na,K-ATPase (a 3 Na+ for 2 K+ ion exchange) is electrogenic, whereas the closely related gastric and non-gastric H,K-ATPases perform electroneutral cation exchange. We have studied the role of a highly conserved serine residue in the fifth transmembrane segment of the Na,K-ATPase, which is replaced with a lysine in all known H,K-ATPases. Ouabain-sensitive 86Rb uptake and K+-activated currents were measured in Xenopus oocytes expressing the Bufo bladder H,K-ATPase or the Bufo Na,K-ATPase in which these residues, Lys800 and Ser782, respectively, were mutated. Mutants K800A and K800E of the H,K-ATPase showed K+-stimulated and ouabain-sensitive electrogenic transport. In contrast, when the positive charge was conserved (K800R), no K+-induced outward current could be measured, even though rubidium transport activity was present. Conversely, the S782R mutant of the Na,K-ATPase had non-electrogenic transport activity, whereas the S782A mutant was electrogenic. The K800S mutant of the H,K-ATPase had a more complex behavior, with electrogenic transport only in the absence of extracellular Na+. Thus, a single positively charged residue in the fifth transmembrane segment of the alpha-subunit can determine the electrogenicity and therefore the stoichiometry of cation transport by these ATPases. |
| Databáze: | OpenAIRE |
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