Nascent helix in the multiphosphorylated peptide αS2-casein(2-20)

Sequence-specific nuclear magnetic resonance (NMR) assignments have been determined for the peptide alpha(S2)-CN(2-20) containing the multiphosphorylated motif-(8)Ser(P)-Ser(P)-Ser(P)-Glu-Glu(12)- 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 Ha chemical shifts. Molecular modelling of the peptide based on these constraints suggests a nascent helix for residues Ser(P)9 to Glu(12). The spectral data for alpha(S2)-CN(2-20) were compared with those of other casein phosphopeptides beta-CN(1-25) and alpha(S1)-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. Copyright (C) 2003 European Peptide Society and John Wiley Sons, Ltd.