Structural and conformational study of the aluminum-thymulin complex using 1-D and 2-D NMR techniques

The interaction between aluminum and thymulin, a linear nonapeptide of thymic origin isolated from serum, was investigated by means of one- and two-dimensional NMR experiments. These experiments were performed in dimethyl-d/sub 6/ sulfoxide solution at different metal:peptide ratios. The results lead the following conclusions: (i) the Al(III) complexation corresponds to a fast exchange on the NMR time scale; (ii) the evolution of /sup 1/H and /sup 13/C NMR chemical shifts indicates the existence of one type of complex with a 1:2 stoichiometry, associating two peptide molecules and one Al(III) ion; (iii) analysis of the spectra suggests that Al(III) has a specific binding site involving the Asn/sup 9/COO/sup /minus// terminal group and the hydroxyl group of the Ser/sup 4/ residue; (iv) from the NOESY data a conformation has been proposed and compared to the biologically active Zn(II)-thymulin complex. 23 refs., 6 figs., 1 tab.