Journal
ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY
Volume 71, Issue -, Pages 1272-1283Publisher
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S1399004715005507
Keywords
backbone geometry; conformational dependences; peptide-bond resonance; bond distances
Funding
- MIUR [PRIN 2010ERFKXL]
- Regione Campania [Legge 5/2007]
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By combining quantum-mechanical analysis of small model peptides and statistical surveys of high-resolution protein structures, a systematic conformational dependence of bond lengths in polypeptide backbones has been unveiled which involves both the peptide bond (C-O and C-N) and those bonds centred on the C-alpha atom. All of these bond lengths indeed display a systematic variability in the psi angle according to both calculations and surveys of protein structures. The overall agreement between the computed and the statistical data suggests that these trends are essentially driven by local effects. The dependence of C-alpha distances on psi is governed by interactions between the sigma system of the C-alpha moiety and the C-O pi system of the peptide bond. Maximum and minimum values for each bond distance are found for conformations with the specific bond perpendicular and parallel to the adjacent CONH peptide plane, respectively. On the other hand, the variability of the C-O and C-N distances is related to the strength of the interactions between the lone pair of the N atom and the C-O pi* system, which is modulated by the psi angle. The C-O and C-N distances are related but their trends are not strictly connected to peptide-bond planarity, although a correlation amongst all of these parameters is expected on the basis of the classical resonance model.
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