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.