NMR studies of the fifth transmembrane segment of Na+,K+-ATPase reveals a non-helical ion-binding region.
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.
Underhaug
Jarl
J
Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Jakobsen
Louise Odgaard
LO
Esmann
Mikael
M
Malmendal
Anders
A
Nielsen
Niels Chr
NC
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*
D007477:Ions; D010455:Peptides; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium