Activation of Platinum(IV) Prodrugs by Cytochrome <i>c</i> and Characterization of the Protein Binding Sites

Platinum­(IV) complexes generally require reduction to reactive Pt­(II) species to exert their chemotherapeutic activity. The process of reductive activation of <sup>15</sup>N-labeled (<i>OC</i>-6–43)-bis­(acetato)­diamminedichloridoplatinum­(IV), in the presence of nicotinamide adenine dinucleotide (NADH) and horse heart cytochrome <i>c</i> (cyt <i>c</i>), was monitored by <sup>1</sup>H,<sup>15</sup>N-HSQC NMR spectroscopy and protein digestion experiments. It has been shown that cyt <i>c</i> plays a catalytic role in the transfer of two reducing equivalents from NADH to Pt­(IV) species. Noncovalent interactions between reduced monoaqua cisplatin (<i>cis</i>-[PtCl­(<sup>15</sup>NH<sub>3</sub>)<sub>2</sub>(H<sub>2</sub>O)]<sup>+</sup>) and the protein, in the proximity of the heme cofactor, and also covalent binding of platinum to the protein region around Met65 and Met80 take place.