Protein recognition of gold-based drugs: 3D structure of the complex formed when lysozyme reacts with Aubipy^c

The structure of the adduct formed in the reaction between Aubipyc, a cytotoxic organogold(III) compound, and the model protein hen egg white lysozyme (HEWL) has been solved by X-ray crystallography. It emerges that Aubipyc, after interaction with HEWL, undergoes reduction of the gold(III) center followed by detaching of the cyclometalated ligand; the resulting naked gold(I) ion is found bound to the protein at Gln121. A direct comparison between the present structure and those previously solved for the lysozyme adducts with other gold(III) compounds demonstrates that coordinated ligands play a key role in the protein–metallodrug recognition process. Structural data support the view that gold(III)-based antitumor prodrugs are activated through metal reduction