Occurrence and role ofcis peptide bonds in protein structures

1H-Nmr was used to measure the rate of cis–trans interconversion of X-Pro bonds in linear and cyclic oligopeptides. k(cis → trans) = 2.5 × 10−3 s−1 at 25°C was found for the zwitterionic form of H-Ala-Pro-OH, in good agreement with earlier measurements. Replacement of Ala by Phe, Tyr, or Trp resulted in a 10-fold slower interconversion rate, whereas after substitution of Ala by His or Glu, the rate decreased only slightly. Independent of the residues X, the interconversion rate was increased by a factor of ca. 20 when the peptide chain was elongated by addition of Ala to the C-terminal Pro. An additional increase by a factor of 6 was observed when going from the protected linear peptide CF3CO-Gly-Gly-Pro-Ala-OCH3 to the closely related cyclic compound c[-Gly-Gly-Pro-Gly-Ala-]. These data are evaluated with regard to their possible use in future studies on the role of X-Pro cis–trans isomerization in the kinetics of protein folding.

Nmr studies of the rates of proline cis–trans isomerization in oligopeptides

Carbon-13-NMR of peptides and proteins

The conformation around the peptide bond between the P1- and P2-positions is important for catalytic activity of some proline-specific proteases.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2874%2980674-5

A novel approach for studies of the molecular conformations in flexible polypeptides

Study of the 1H n.m.r. spectra of the N-acyl-prolines (I) and (II) in deuteriochloroform over a range of temperature has enabled the thermodynamic parameters for the interconversion of such conformers by rotation about the N–CO bond to be evaluated for the first time.

Evaluation of the thermodynamic parameters for the interconversion of the conformational isomers of two N-acyl-prolines by nuclear magnetic resonance spectroscopy

H. N. Rydon

Papers

Evaluation of the thermodynamic parameters for the interconversion of the conformational isomers of two N-acyl-prolines by nuclear magnetic resonance spectroscopy