Human nongastric H+-K+-ATPase: transport properties of ATP1al1 assembled with different beta -subunits

• Published in: American Journal of Physiology: Cell Physiology Vol. 283; no. 1; pp. C305 - C314
• Main Authors: Crambert, Gilles, Horisberger, Jean-Daniel, Modyanov, Nikolai N, Geering, Kathi
• Format: Journal Article
• Language: English
• Published: United States 01.07.2002
• Subjects: 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; Sodium-Potassium-Exchanging ATPase - metabolism; Xenopus
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00590.2001

1  Institute Of Pharmacology And Toxicology of The University, CH-1005 Lausanne, Switzerland; and 2  Department Of Pharmacology, Medical College Of Ohio, Toledo, Ohio 43614-5804 To investigate whether nongastric H + -K + -ATPases transport Na + in exchange for K + and whether different -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 1 -subunit ( 1 ) expressed in Xenopus oocytes, with different -subunits. Our results show that HK and 1 -NK can produce functional AL1/ complexes at the oocyte cell surface that, in contrast to 1 / 1 NK and 1 / HK complexes, exhibit a similar apparent K + affinity. Similar to Na + -K + -ATPase, AL1/ 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 -isoforms influence the protease sensitivity of AL1 and 1 and that AL1/ 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 -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 -subunit. X + -K + -ATPases; Na + transport; Xenopus oocytes; intersubunit interactions