NMR study of a lymphocyte differentiating thymic factor. An investigation of the Zn(II)-nonapeptide complexes (thymulin)

• Published in: The Journal of biological chemistry Vol. 263; no. 12; pp. 5574 - 5580
• Main Authors: Cung, M T, Marraud, M, Lefrancier, P, Dardenne, M, Bach, J F, Laussac, J P
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 25.04.1988; American Society for Biochemistry and Molecular Biology
• Subjects: Biological and medical sciences; Dimethyl Sulfoxide; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Immunobiology; Lymphoid cells: ontogeny, maturation, markers, receptors, circulation and recirculation; Magnetic Resonance Spectroscopy; Oligopeptides - metabolism; Protein Conformation; Solutions; Temperature; Thymic Factor, Circulating - metabolism; Thymus Hormones - metabolism; Zinc - metabolism; Thymus gland; Serum; Molecular complex; NMR spectrometry; Cell differentiation; Lymphocyte; Zinc
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)60603-9

Detailed investigations of a serum peptide (less than Glu1-Ala2-Lys3-Ser4-Gln5-Gly6-Gly7-Ser8-++ +Asn9) were carried out by 1H and 13C NMR spectroscopy to elucidate the structure of the complex formed with Zn(II), thymulin, which has been found to be active in vivo. These experiments were performed in dimethyl sulfoxide-d6 solution at different metal:peptide ratios. The results suggest the following conclusions. (i) The Zn(II) complexation corresponds to a fast exchange on the NMR time scale. (ii) The evolution of 1H and 13C NMR chemical shifts indicates the existence of two types of complexes: a 1:2 species associating two peptide molecules and one Zn(II) ion and a complex with 1:1 stoichiometry. The former is predominant for metal:peptide ratios below unity. (iii) In the 1:2 complex, Zn(II) is coordinated by the Ser4-O gamma H and Asn9-CO2- sites, while in the 1:1 complex, Ser8-O gamma H is the third ligand to the Zn(II) ion. The results are compared with those for the [Ala4] and [Ala8] analogues, and those for the complexes of thymulin with other metal ions (Cu2+ and Al3+) in terms of its biological activity. These comparative studies suggested that the 1:1 complex is the only conformation recognized by the antibodies.