The reaction of a platinated methionine motif of CTR1 with cysteine and histidine is dependent upon the type of precursor platinum complex

Abstract

The human copper protein (hCTR1) is believed to facilitate the cellular uptake of cisplatin. Cisplatin likely binds to the methionine (Met)-rich motifs located in the N-terminus of hCTR1, and ligand exchange would be essential if cisplatin has to pass through the hCTR1 channel. In this work, we investigated the reaction between platinated adducts of a methionine-rich motif of yeast CTR1 (Mets7) and N-acetyl-cysteine (AcCys) or N-acetyl-histidine (AcHis), mimicking metal-binding residues downstream the CTR1 channel. Platination involved two cis-compounds, cisplatin and oxaliplatin, and one monofunctional complex, cis-diammine(pyridine)chloridoplatinum(II) (cDPCP). The reactions were monitored by HPLC and the products were characterized by ESI-MS. The results indicate different reactivities depending upon the platinum complex. The cisplatin/Mets7 adduct reacts readily with both cysteine and histidine (t1/2<2min). In contrast, the oxaliplatin/Mets7 adduct reacts with cysteine but not with histidine, whereas cDPCP/Mets7 adduct reacts with histidine but not with cysteine. Hence, Mets7 adducts of these platinum complexes exhibit different reactivities towards downstream coordinating amino acids. These results suggest that each platinum complex possesses different reactivities and consequently may lead to differences in their cellular distribution and bioactivity.

Keywords: Anticancer drugs; Copper transport proteins; Metal coordination; Platinum complexes; Substitution reactions.