INCOHERENT RELATIONSHIP BETWEEN TORSION VALUES AND BOND LENGTHS IN ATOMIC RESOLUTION PROTEIN CRYSTAL STRUCTURES

Oliviero Carugo

Department of General Chemistry, Pavia University, Viale Taramelli 12, 27100 Pavia, Italy and Protein Structure and Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology, Padrice 99, 34012 Trst, Italy

Abstract

Deviations from planarity of the peptide Ca-C(=O)-N moiety are expected to be accompanied by the lengthening of the C-N and the shortening of the C=O bonds. Surprisingly, such a relationship cannot be detected by an analysis of the atomic resolution protein crystal structures deposited in the Protein Data Bank. This could be due to either an incorrect parameterisation of the refinement restraints or to the large mobility of the protein atoms, which could prevent their exact location.