Membrane disposition of the M5-M6 hairpin of Na+,K+-ATPase α subunit is ligand dependent

Svetlana Lutsenko, Rebecca Anderko, Jack H. Kaplan

Research output: Contribution to journalArticlepeer-review

96 Scopus citations


Extensive proteolytic digestion of Na+,K+-ATPase (EC by trypsin produces a preparation where most of the extramembrane portions of the a subunit have been digested away and the β subunit remains essentially intact. The fragment Gln-737-Arg-829 of the Na+,K+-ATPase α subunit, which includes the putative transmembrane hairpin M5-M6, is readily, selectively, and irreversibly released from the posttryptic membrane preparation after incubation at 37°C for several minutes. Once released from the membrane, the fragment aggregates but remains water soluble. Occlusion of K+ or Rb+ specifically prevents release of the Gln-737-Arg-829 fragment into the supernatant. Labeling of the posttryptic membrane preparation with cysteine- directed reagents revealed that Cys-802 (which is thought to be located within the M6 segment) is protected against the modification by Rb+ while this fragment is in the membrane but ran be readily modified upon release. Cation occlusion apparently alters the folding and/or disposition of the MS- M6 fragment in the membrane in a way that does not occur when the fragment migrates to the aqueous phase. The ligand-dependent disposition of the M5-M6 hairpin in the membrane along with recent labeling studies suggest a key role for this segment in cation pumping by Na+,K+-ATPase.

Original languageEnglish (US)
Pages (from-to)7936-7940
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
StatePublished - Aug 15 1995
Externally publishedYes


  • cation occlusion
  • membrane topology
  • transmembrane segments

ASJC Scopus subject areas

  • General


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