[Particularities of Spatial Organization of Human Hemokinin-1 and Mouse/Rat Hemokinin-1 Molecules]

By molecular mechanics method the conformational properties of two molecules of the tachykinin family, human hemokinin-1 and mouse/rat hemokinin-1, each consisting of 11 amino acids, have been investigated. On the basis of a step-by-step approach we determined the energetically favorable spatial structures of these molecules and their fragments represented as a set of conformations characterized by the relatively labile N-terminal tripeptide and conformationally rigid C-terminal segment. It was shown that conformationally conservative C-terminal octapeptide of the molecules preferably forms two conformations with different structural types of the peptide chain. One of these conformations has an alpha-helical structure, and the other forms the chain's turn that led to an alpha helical turn at the C-terminus. As a result of calculations the energetically favorable ranges of the values of the dihedral angles and orientations of all the residues in low energy conformational states of the molecules were shown. Due to conformational analysis of separate fragments it was possible to trace the process of the second structure formation in these molecules. Based on the results obtained the contribution of inter-residues interaction energy was determined and the role of the each residue in the formation of the optimal spatial structures of hemokinin-1 molecules was estimated.