Activation of Platinum(IV) Prodrugs by Cytochrome c 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 ¹⁵N-labeled (OC-6–43)-bis­(acetato)­diamminedichloridoplatinum­(IV), in the presence of nicotinamide adenine dinucleotide (NADH) and horse heart cytochrome c (cyt c), was monitored by ¹H,¹⁵N-HSQC NMR spectroscopy and protein digestion experiments. It has been shown that cyt c plays a catalytic role in the transfer of two reducing equivalents from NADH to Pt­(IV) species. Noncovalent interactions between reduced monoaqua cisplatin (cis-[PtCl­(¹⁵NH₃)₂(H₂O)]⁺) 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.