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extremely mild set of conditions required for this rearrangement, suggesting that analogous processes might occur in biological systems. Acknowledgment. We wish to thank Dr. Koshiro Toriumi of the Institute for Molecular Science and Dr. Kiyotaka Asakura of the Faculty of Science, University of Tokyo, for their technical assistance and helpful suggestions during the course of EXAFS measurements and analysis and Dr. Nobuyuki Watanabe for
detecting ketoses in HPLC analysis. This work was partially supported by Grants-in-Aid for Scientific Research from the Ministry of Education of Japan (63107002,63470035,63612002), and by a grant-in-aid from the Mitsubishi Foundation. Supplementary Material Available: Plots of background-subtracted raw EXAFS data (k3[x(k)])and the results of curve fitting (observed vs calculated EXAFS oscillations) (4 pages). Ordering information is given on any current masthead page.
Contribution from the Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France, Institut Choay, 46 avenue Th. Gautier, 75016 Paris, France, HBpital Necker, INSERM U25, 16 rue de SEvres, 75730 Paris, France, and UA 494 du CNRS, ENSIC-INPL, 54042 Nancy Cedex, France
Structural and Conformational Study of the Aluminum-Thymulin Complex Using 1-D and 2-DNMR Techniques J.-P. Laussac,*,+ P. Lefrancier,f M. Dardenne,g J.-F. Bath,§ M. Marraud," a n d M.-T. Cung" Received December 15, 1987 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-d6sulfoxide solution at different metakpeptide ratios. The results lead the following conclusions: (i) the AI(II1) complexation corresponds to a fast exchange on the NMR time scale; (ii) the evolution of IH and "C NMR chemical shifts indicates the existence of one type of complex with a 1:2 stoichiometry, associating two peptide molecules and one Al(II1) ion; (iii) analysis of the spectra suggests that AI(II1) has a specific binding site involving the AsngCOO- terminal group and the hydroxyl group of the Ser4 residue; (iv) from the NOESY data a conformation has been proposed and compared to the biologically active Zn(I1)-thymulin complex. tually devoid of biological activity. Introduction To this end, we have attempted to obtain information on the Thymulin, formerly called FTS (for facteur thymique scrique), conformational states of the nonapeptide-aluminum complex in is a thymic hormone isolated from which has been dimethyl sulfoxide solution by means of the 'H, 13C, 27Al onecharacterized by its capacity to induce T-cell markers and and two-dimensional (IH, 'H NOESY) N M R spectroscopy. functions on immature cells3 Its amino acid sequence was From analyses of the spectral data, it is concluded that A13+ determined to be > 1 ) corresponding to proteins studied at high field and the fast motion limit (W,,T~85% is present and where a mixing time of 350 ms is used in order to avoid the perturbation of the spin-diffusion phenomena. Furthermore, observation of the behavior of the free-peptide 2-D spectra9 would immediately suggest that the complexation of thymulin with aluminum is of quite a different nature compared to that of the nonapeptide. In light of these arguments, it would seem that the observed off-diagonal peaks in the NOESY map (Figure 4) correspond
+
M. A,; Rico, M.; Herranz, J.; Santoro, J.; Nieto, J. L. Paper presented at the 2%meForum Peptides, Nancy, France, 1988. (1 3) Picone, D.; Tenussi, P. A,; Marastoni, M.; Tomatis, R.; Motta, A. FEBS Lett. 1988, 231, 159-163. (14) Cung, M.-T.; Legros, E.; Vitoux, B. Unpublished data.
(12) Jimenez,
NMR Study of the Aluminum-Thymulin Complex
Inorganic Chemistry, Vol. 27, No. 23, 1988 4097
Table I. "C NMR Internal Chemical Shifts between FTS Bound to AI(II1) and Its Free Form in DMSO-dn resonance A,. ppm resonance A,' ppm resonance A: ppm
