NMR and CD studies of triple‐helical peptides

Abstract

Triple-helix formation of the peptide (Pro-Hyp-Gly)₁₀ was monitored by nmr and CD spectroscopy. The two-dimensional nmr spectra indicated that the Gly Cα H and Pro CδH proton resonances shift upfield in going from the nonhelical to helical form, while hydroxyproline resonances are unchanged. The integrated areas of the helical and nonhelical resonances could be monitored in the one-dimensional nmr spectrum, and indicate that in the (Pro-Hyp-Gly)₁₀ about 90% of the residues are in a defined triple-helical conformation. The introduction of a glycine to alanine substitution or the deletion of a single hydroxyproline residue in the stable triple-helical peptide (Pro-Hyp-Gly)₁₀ still allows trimers to be formed, but the trimers show a substantial loss of triple helix and decreased thermal stability compared with (Pro-Hyp-Gly)₁₀. Two computer models were generated for the Gly → Ala peptide, one with the Ala side chains packed inside the helix and the other with the region containing the alanines forming a β-bend that loops out from the helix. The nmr data is more consistent with the latter model.