Conformational aspects in the formation of structures of the backbone of polypeptide chains in proteins. Relationship between conformational stability/lability and β-turns

Abstract

To assess the nature of the relationship between the integral conformational stability of tetrapeptides and the main types of β-turns (which are also tetrapeptides), calculations were performed using spectrum diagrams and asymmetry in the distribution of conformationally stable and unstable tetrapeptides. It was shown that type I', II, and II' β-turns are comprised of predominantly conformationally labile peptides, that is consistent with the predetermined nature of their structure as described earlier. As previously shown in our study, in this case the conformation is imposed by external conditions (namely the cycle closuring) and the prevalence of conformationally labile peptides facilitates the formation of the structure by virtue of external factors. Type I β-turn is an exception: peptides with different conformational lability are fairly evenly distributed. Most likely, this indicates that the formation of the type I β-turn is not predetermined.