A software tool for the prediction of Xaa-Pro peptide bond conformations in proteins based on 13C chemical shift statistics

The chemical shift difference (delta[C-13(beta)] - delta[C-13]) is a reference-independent indicator of the Xaa-Pro peptide bond conformation. Based on a statistical analysis of the C-13 chemical shifts of 1033 prolines from 304 proteins deposited in the BioMagRes database, a software tool was created to predict the probabilities for cis or trans conformations of Xaa-Pro peptide bonds. Using this approach, the conformation at a given Xaa-Pro bond can be identified in a simple NOE-independent way immediately after obtaining its NMR resonance assignments. This will allow subsequent structure calculations to be initiated using the correct polypeptide chain conformation.