title: Conformation of the cytoplasmic domain of phospholamban by NMR and CD.
abstract: Nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy have been used to characterize the conformation of the putative cytoplasmic domain of phospholamban (PLB), an oligomeric membrane-bound protein which regulates the activity of the cardiac sarcoplasmic reticulum Ca(2+)-dependent ATPase. In aqueous solution the 25-residue peptide adopts a number of rapidly interconverting conformers with no secondary structural type obviously predominating. However, in trifluoroethanol (TFE) the conformation, while still highly dynamic, is characterized by a high proportion of helical structures. Evidence for this is provided by alpha CH chemical shifts and low NH chemical shift temperature coefficients, small NH-alpha CH intraresidue scalar coupling constants, a substantial number of distinctive interresidue nuclear Overhauser effects (NOEs) [dNN(i, i + 1), d alpha N(i, i + 3), d alpha beta(i, i + 3) and d alpha N(i, i + 4)] and characteristic CD bands at 190 (positive), 206 (negative) and 222 nm (negative). The helicity is interrupted around Pro-21. The activity of PLB is regulated by phosphorylation at either Ser-16 or Thr-17. CD shows that phosphorylation at Ser-16 by the cAMP-activated protein kinase causes about an 11% decrease in alpha-helical content in TFE.
authors.affiliation: SmithKline Beecham Pharmaceuticals, Harlow, Essex, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Hubbard
authors.forename: L K
authors.initials: LK
authors.lastname: MacLachlan
authors.forename: E
authors.initials: E
authors.lastname: Meenan
authors.forename: C J
authors.initials: CJ
authors.lastname: Salter
authors.forename: D G
authors.initials: DG
authors.lastname: Reid
authors.forename: P
authors.initials: P
authors.lastname: Lahouratate
authors.forename: J
authors.initials: J
authors.lastname: Humphries
authors.forename: N
authors.initials: N
authors.lastname: Stevens
authors.forename: D
authors.initials: D
authors.lastname: Bell
authors.forename: W A
authors.initials: WA
authors.lastname: Neville
mesh_terms: D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D002942:Circular Dichroism; D003593:Cytoplasm / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D010766:Phosphorylation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012694:Serine / Q000737:chemistry; D000099211:Phospholamban
chemical_list: D000251:Adenosine Triphosphatases; D002135:Calcium-Binding Proteins; D010446:Peptide Fragments; D012694:Serine; D000099211:Phospholamban