title: Nascent helix in the multiphosphorylated peptide alphaS2-casein(2-20).
abstract: Sequence-specific nuclear magnetic resonance (NMR) assignments have been determined for the peptide alphaS2-CN(2-20) containing the multiphosphorylated motif-8Ser(P)-Ser(P)-Ser(P)-Glu-Glu12- in the presence of molar excess Ca2+. The secondary structure of the peptide was characterized by sequential (i,i + 1), medium-range (i,i + 2/3/4) nOes and H alpha chemical shifts. Molecular modelling of the peptide based on these constraints suggests a nascent helix for residues Ser(P)9 to Glu12. The spectral data for alphaS2-CN(2-20) were compared with those of other casein phosphopeptides beta-CN(1-25) and alphaS1-CN(59-79) that also contain the multiphosphorylated motif. This comparison revealed a similar pattern of secondary amide chemical shifts in the multiphosphorylated motif. However, the patterns of medium-range nOe connectivities in the three peptides suggests they have distinctly different conformations in the presence of Ca2+ despite having a high degree of sequential similarity.
authors.affiliation: School of Dental Science, The University of Melbourne, 711 Elizabeth Street, Melbourne, 3000, Victoria, Australia.
authors.forename: N Laila
authors.initials: NL
authors.lastname: Huq
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Cross
authors.forename: Eric C
authors.initials: EC
authors.lastname: Reynolds
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000494:pharmacology; D002364:Caseins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010748:Phosphopeptides / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects
chemical_list: D002364:Caseins; D010446:Peptide Fragments; D010748:Phosphopeptides; D002118:Calcium