Studies on the conformation of amino acids III. Backbone conformation of N-and C-terminal glycyl and alanyl residues

Abstract

Potential energy calculations were carried out to determine the possible conformations of N-and C-terminal glycyl and alanyl residues. Non-bonded and electrostatic contributions to the conformational energies were obtained and their role in predicting the favourable conformations has been assessed. It is shown that in the case of glycyl and alanyl N-terminal residues, a conformation in which the plane of the amide group is nearly coplanar with the plane through the backbone atoms N, C, and C is the most favourable one and this conformation is mainly stabilized by the electrostatic interactions. The results also indicate that the backbone conformation of all the N-terminal residues with various side chains are nearly the same and could be shown to be that of glycyl and alanyl N-terminal residues. The importance of the coplanarity of the amide and the carboxyl groups and so also their perpendicular orientation in the C-terminal residues is stressed.