Structural-Functional Organization of the Neurokinin A and Neurokinin B Molecules: I. Theoretical Conformational Analysis of Neurokinin A

The spatial structure of the neurokinin A molecule under the conditions of a polar medium was studied by theoretical conformational analysis. Segmental analysis determined stable structures of the decapeptideamide neurokinin A, which can be represented as four families of conformations characterized by the relatively labile N-terminal tripeptide and the conformationally rigid C-terminal heptapeptide. It was shown that the neurokinin A molecule preferably forms two virtually isoenergetic conformations with different structural types of the peptide chain. One of the conformations has a fully alpha -helical structure, and the other forms two beta turns at the N terminus and an alpha -helical turn at the C terminus.