title: NMR studies of the fifth transmembrane segment of Na+,K+-ATPase reveals a non-helical ion-binding region.
abstract: The structure of a synthetic peptide corresponding to the fifth membrane-spanning segment (M5) in Na(+),K(+)-ATPase in sodium dodecyl sulfate (SDS) micelles was determined using liquid-state nuclear magnetic resonance (NMR) spectroscopy. The spectra reveal that this peptide is substantially less alpha-helical than the corresponding M5 peptide of Ca(2+)-ATPase. A well-defined alpha-helix is shown in the C-terminal half of the peptide. Apart from a short helical stretch at the N-terminus, the N-terminal half contains a non-helical region with two proline residues and sequence similarity to a non-structured transmembrane element of the Ca(2+)-ATPase. Furthermore, this region spans the residues implicated in Na(+) and K(+) transport, where they are likely to offer the flexibility needed to coordinate Na(+) as well as K(+) during active transport.
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
authors.forename: Jarl
authors.initials: J
authors.lastname: Underhaug
authors.forename: Louise Odgaard
authors.initials: LO
authors.lastname: Jakobsen
authors.forename: Mikael
authors.initials: M
authors.lastname: Esmann
authors.forename: Anders
authors.initials: A
authors.lastname: Malmendal
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D007477:Ions / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D007477:Ions; D010455:Peptides; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium