X-ray structure of the ternary complex Zn(II)-ATP-2,2'-bipyridyl a possible model for ATP transport

Ternary complexes between metal ions, nucleotides and aromatic heterocyclic amines are being investigated by X-ray diffraction as possible models for enzyme–metal–substrate interactions1,2. Kennard and coworkers3 have reported the crystal structure of the ATP disodium salt. Although more recently several crystal structures of binary and ternary complexes between metal ions and nucleoside monophosphates have been reported, no structure combining metal complexes with nucleoside di- or triphosphates has been reported. Most divalent metal ions catalyse the nonenzymatic transfer of phosphate from nucleoside polyphosphates to various acceptors4. Therefore, these compounds in water solution undergo extensive hydrolysis in the presence of metal ions, leading to the formation of the monophosphates; for instance, at pH 6.5, Cu2+ accelerates the hydrolysis of ATP by a factor of about 300 (ref. 5). We report here the crystal and molecular structure of the complex [Zn(II)-H2ATP-2,2'-bipyridyl]2dot4H2O, determined by single crystal X-ray analysis. The complex molecule provides a possible model for ATP transport and phosphate group transfer mechanism.