Article: article from journal or magazin.
Human nongastric H+-K+-ATPase: transport properties of ATP1al1 assembled with different beta-subunits.
American Journal of Physiology. Cell Physiology
Publication types: Journal Article
To investigate whether nongastric H+-K+-ATPases transport Na+ in exchange for K+ and whether different beta-isoforms influence their transport properties, we compared the functional properties of the catalytic subunit of human nongastric H+-K+-ATPase, ATP1al1 (AL1), and of the Na+-K+-ATPase alpha1-subunit (alpha1) expressed in Xenopus oocytes, with different beta-subunits. Our results show that betaHK and beta1-NK can produce functional AL1/beta complexes at the oocyte cell surface that, in contrast to alpha1/beta1 NK and alpha1/betaHK complexes, exhibit a similar apparent K+ affinity. Similar to Na+-K+-ATPase, AL1/beta complexes are able to decrease intracellular Na+ concentrations in Na+-loaded oocytes, and their K+ transport depends on intra- and extracellular Na+ concentrations. Finally, controlled trypsinolysis reveals that beta-isoforms influence the protease sensitivity of AL1 and alpha1 and that AL1/beta complexes, similar to the Na+-K+-ATPase, can undergo distinct K+-Na+- and ouabain-dependent conformational changes. These results provide new evidence that the human nongastric H+-K+-ATPase interacts with and transports Na+ in exchange for K+ and that beta-isoforms have a distinct effect on the overall structural integrity of AL1 but influence its transport properties less than those of the Na+-K+-ATPase alpha-subunit.
Animals, Biological Transport/physiology, Cell Membrane/metabolism, Enzyme Activation/drug effects, Enzyme Inhibitors/pharmacology, H(+)-K(+)-Exchanging ATPase/chemistry, H(+)-K(+)-Exchanging ATPase/metabolism, Humans, Isoenzymes/metabolism, Ligands, Molecular Conformation, Oocytes, Ouabain/pharmacology, Peptide Hydrolases/metabolism, Potassium/pharmacology, Protein Processing, Post-Translational, Sodium-Potassium-Exchanging ATPase/chemistry, Sodium-Potassium-Exchanging ATPase/drug effects, Xenopus
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