Correlation between biological activity and conformational dynamics properties of tetra- and pentapeptides derived from fetoplacental proteins.

In this work, using molecular dynamics simulation, we study conformational and dynamic properties of biologically active penta- and tetrapeptides derived from fetoplacental proteins such as alpha-fetoprotein, pregnancy specific β1-glycoprotein, and carcinoembryonic antigen. Existence of correlation between flexibility of peptide backbone and biological activity of the investigated peptides was shown. It was also demonstrated that flexibility of peptide backbone depends not only on its length, but also on the presence of reactive functional groups in amino acid side chains that participate in intramolecular interactions. Peptides that demonstrate similar biological effects in regulation of proliferation of lymphocytes and expression of differentiation antigens on their surface (LDSYQCT, PYECE, YECE, and YVCE) are characterized by rigidity of their peptide backbone. Increased backbone flexibility in peptides PYQCE, YQCE, SYKCE, YQCT, YQCS, YVCS, YACS, and YACE is correlated with decreased biological activity. Conformational mobility of amino acid residues does not depend on physicochemical properties only, but also on intramolecular interactions. So, evolutionary restrictions should exist to maintain such interactions in the environment of functionally important sites.