Peptide-bond distortions and the curvature of α-helices

✍ Scribed by P. Chakrabarti; M. Bernard; D. C. Rees

• Publisher: Wiley (John Wiley & Sons)
• Year: 1986
• Tongue: English
• Weight: 349 KB
• Volume: 25
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360250609

✦ Synopsis

A ngeles, Los A nge les, California 90024

Synopsis

Solvent accessible peptide bonds in proteins exhibit a 1-3" compression of the OCN bond angle and a corresponding expansion of the NCCa bond angle, relative to buried peptide bonds. These changes are consistent with an increase in hydrogen bonding to the carbonyl oxygen accompanying solvent exposure (J. D. Dunitz and F. K. Winkler, (1975) Acta Cryst. B31, 251-263). For amphiphilic structures such as a-helices, systematic differences in peptide-bond geometry between solventexposed and buried residues will generate significant curvature. A decrease of 4" in the OCN bond angle between hydrophilic and hydrophobic sides,of an Fmphiphilic helix will lead to smooth bending, with a radius of curvature of about 70 A. This curvature is in the range observed for a-helices in proteins. Helix curvature is estimated to have only a small effect on the magnitude and direction of the helical dipole moment.