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 N-15-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 H-1,N-15-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((NH3)-N-15)(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.