C-terminal capping motifs in model helical peptides.
Solution structures of a series of consensus sequence peptides with N- and C-terminal capping interactions have been determined by 2-D nuclear magnetic resonance spectroscopy and a simulated annealing strategy. All peptides are found to be stabilized by a hydrophobic interaction and a capping box structure (SXXE) at the N-terminus whereas several different capping motifs are discerned near the peptide C-terminus. Among these, the asparagine side chain-backbone main chain (i, i-4) capping structure is most stabilizing and highly populated in the simulated annealing calculation. A glycine alphaL capping motif stabilizes the peptide terminus, which otherwise tends to fray, but this is occupied only a fraction of the time in the trial structures determined. Our experimental search over several models for a second type of C-terminal capping structure, the so-called 'Schellman motif', which is seen in native proteins, is unsuccessful, indicating this structural element contributes less to oligopeptide stability in solution and most probably populates only transiently.
Kallenbach
N R
NR
Department of Chemistry, New York University, NY 10003, USA. kallnbch@is.nyu.edu
Gong
Y
Y
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry
D010455:Peptides; D011506:Proteins