title: NMR studies of the fifth transmembrane segment of sarcoplasmic reticulum Ca2+-ATPase reveals a hinge close to the Ca2+-ligating residues.
abstract: Two recent X-ray structures have tremendously increased the understanding of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and related proteins. Both structures show the fifth transmembrane span (M5) as a single continuous alpha-helix. The inherent structural and dynamic features of this span (Lys758-Glu785) were studied in isolation in sodium dodecyl sulfate (SDS) micelles using liquid-state nuclear magnetic resonance (NMR) spectroscopy. We find that a flexible region (Ile765-Asn768) is interrupting the alpha-helix. The location of the flexible region near the Ca(2+) binding residues Asn768 and Glu771 suggests that together with a similar region in M6 it has a hinge function that may be important for cooperative Ca(2+) binding and occlusion.
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology, University of Aarhus, Langelandsgade 140, Denmark.
authors.forename: Gerd
authors.initials: G
authors.lastname: Nielsen
authors.forename: Anders
authors.initials: A
authors.lastname: Malmendal
authors.forename: Axel
authors.initials: A
authors.lastname: Meissner
authors.forename: Jesper V
authors.initials: JV
authors.lastname: Møller
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry; D007425:Intracellular Membranes / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate
chemical_list: D008051:Lipid Bilayers; D008823:Micelles; D010455:Peptides; D012967:Sodium Dodecyl Sulfate; D018698:Glutamic Acid; D000252:Calcium-Transporting ATPases; D008239:Lysine; D002118:Calcium