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  Functional Significance of E2 State Stabilization by Specific α/β-Subunit Interactions of Na,K- and H,K-ATPase

Dürr, K. L., Tavraz, N. N., Dempski, R. E., Bamberg, E., & Friedrich, T. (2009). Functional Significance of E2 State Stabilization by Specific α/β-Subunit Interactions of Na,K- and H,K-ATPase. The Journal of Biological Chemistry, 284(6), 3842-3854. doi:10.1074/jbc.M808101200.

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 Creators:
Dürr, Katharina L.1, Author
Tavraz, Neslihan N.1, Author
Dempski, Robert E.2, Author              
Bamberg, Ernst2, 3, Author              
Friedrich, Thomas1, Author
Affiliations:
1Technical University of Berlin, Institute of Chemistry, 10623 Berlin, Germany, ou_persistent22              
2Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society, ou_2068289              
3Johann Wolfgang Goethe-University Frankfurt, Chemical and Pharmaceutical Sciences Department, 60439 Frankfurt am Main, Germany, ou_persistent22              

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 Abstract: The β-subunits of Na,K-ATPase and H,K-ATPase have important functions in maturation and plasma membrane targeting of the catalytic α-subunit but also modulate the transport activity of the holoenzymes. In this study, we show that tryptophan replacement of two highly conserved tyrosines in the transmembrane domain of both Na,K- and gastric H,K-ATPase β-subunits resulted in considerable shifts of the voltage-dependent E1P/E2P distributions toward the E1P state as inferred from presteady-state current and voltage clamp fluorometric measurements of tetramethylrhodamine-6-maleimide-labeled ATPases. The shifts in conformational equilibria were accompanied by significant decreases in the apparent affinities for extracellular K+ that were moderate for the Na,K-ATPase β-(Y39W,Y43W) mutation but much more pronounced for the corresponding H,K-ATPase β-(Y44W,Y48W) variant. Moreover in the Na,K-ATPase β-(Y39W,Y43W) mutant, the apparent rate constant for reverse binding of extracellular Na+ and the subsequent E2P-E1P conversion, as determined from transient current kinetics, was significantly accelerated, resulting in enhanced Na+ competition for extracellular K+ binding especially at extremely negative potentials. Analogously the reverse binding of extracellular protons and subsequent E2P-E1P conversion was accelerated by the H,K-ATPase β-(Y44W,Y48W) mutation, and H+ secretion was strongly impaired. Remarkably tryptophan replacements of residues in the M7 segment of Na,K- and H,K-ATPase α-subunits, which are at interacting distance to the β-tyrosines, resulted in similar E1 shifts, indicating their participation in stabilization of E2. Thus, interactions between selected residues within the transmembrane regions of α- and β-subunits of P2C-type ATPases exert an E2-stabilizing effect, which is of particular importance for efficient H+ pumping by H,K-ATPase under in vivo conditions.

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Language(s): eng - English
 Dates: 2008-11-242008-10-222008-12-082009-02-06
 Publication Status: Published in print
 Pages: 13
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1074/jbc.M808101200
PMID: 19064992
 Degree: -

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Title: The Journal of Biological Chemistry
  Other : JBC
  Abbreviation : J. Biol. Chem.
Source Genre: Journal
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Publ. Info: Baltimore, etc. : American Society for Biochemistry and Molecular Biology [etc.]
Pages: - Volume / Issue: 284 (6) Sequence Number: - Start / End Page: 3842 - 3854 Identifier: ISSN: 0021-9258
CoNE: https://pure.mpg.de/cone/journals/resource/954925410826_1