NMR Study Of The Interactions Between ATP And Some Metal Ions

Adenosine-5'-triphosphate (ATP) is very important in metabolism. It plays a significant role in many enzymatic reactions, especially in the presence of some metal ions. The binding site of ATP in solution with metal ions is a key factor affecting their biological functions Therefore, it is of great interest to study the conformations of ATP-metal ion complexes. The complexes can show their biological activity only in solutions. Modern Nuclear Magnetic Resonance (NMR) is a powerful technique to investigate molecular interactions in solutions and give information about the conformation of the complexes at the molecular level.Not long before it had been found that the conformation of ATP complexes with Fe³⁺ and Zn²⁺ was very sensitive to the pH of the solutions. Hence we undertook the study of the interactions between ATP and Mg²⁺, Cd²⁺, Pt²⁺ to see whether the pH dependent conformation is common to other metal ions. In this dissertation the binding site of these metal ions at ATP has been investigated by NMR and necessary computation. Different conformations have been identified in the solution at different pHs.The concept of base stacking of nucleotides in solutions had been well accepted. However, direct evidence had not been reported. In our experiments, the intermolecular NOE cross peaks between ATP and GTP were observed for the first time, which unambiguously indicated the base stacking of nucleotides in solutions.The conformation of the complex of ATP-Mg²⁺ has been studied thoroughly by NMR experiments on ATP in the absence and presence of MgCl₂ in a wide pH range from 1 to 10. The large ¹⁵N chemical shift change (up to 10 ppm) around pH 3.7 observed in our experiments and the systematic ³¹P observations suggest that ATP interacts with Mg²⁺ via N1 of adenine, simultaneously with the phosphate chain To seek the evidence of the N1-binding interaction, NOESY (Nuclear Overhauser Effect SpectroscopY) experiments have been performed on ATP in the presence of 1:1 Mg²⁺...