title: Helical structure of phospholamban in membrane bilayers.
abstract: The regulation of calcium levels across the membrane of the sarcoplasmic reticulum involves the complex interplay of several membrane proteins. Phospholamban is a 52 residue integral membrane protein that is involved in reversibly inhibiting the Ca(2+) pump and regulating the flow of Ca ions across the sarcoplasmic reticulum membrane during muscle contraction and relaxation. The structure of phospholamban is central to its regulatory role. Using homonuclear rotational resonance NMR methods, we show that the internuclear distances between [1-(13)C]Leu7 and [3-(13)C]Ala11 in the cytoplasmic region, between [1-(13)C]Pro21 and [3-(13)C]Ala24 in the juxtamembrane region and between [1-(13)C]Leu42 and [3-(13)C]Cys46 in the transmembrane domain of phospholamban are consistent with alpha-helical secondary structure. Additional heteronuclear rotational-echo double-resonance NMR measurements confirm that the secondary structure is helical in the region of Pro21 and that there are no large conformational changes upon phosphorylation. These results support the model of the phospholamban pentamer as a bundle of five long alpha-helices. The long extended helices provide a mechanism by which the cytoplasmic region of phospholamban interacts with residues in the cytoplasmic domain of the Ca(2+) pump.
authors.affiliation: Department of Biochemistry and Cell Biology, Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, NY 11794-5115, USA. steven.o.smith@sunysb.edu
authors.forename: S O
authors.initials: SO
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: Kawakami
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Ziliox
authors.forename: S
authors.initials: S
authors.lastname: Aimoto
mesh_terms: D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012399:Rotation; D017550:Spectroscopy, Fourier Transform Infrared; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D004134:Dimyristoylphosphatidylcholine; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D000099211:Phospholamban; C028694:1-palmitoyl-2-oleoylphosphatidylcholine