Supramolecular Cadmium‐Telluride Proteoliposomal Assemblies for Real‐Time Detection of Protein‐Catalyzed Pt(II)‐Complexes Transmembrane Translocation: Cu(I)‐Pumps Are Electrogenic Pt(II)‐Drug Uniporters

ABSTRACT Overexpression of transmembrane Cu(I) P‐type ATPase pumps in cancer cells correlates with drug resistance towards chemotherapeutic Pt(II)‐based drugs, suggesting that they may facilitate the vesicular sequestration and cellular efflux of Pt(II)‐complexes. However, the ability of Cu(I)‐pumps to translocate Pt(II)‐drugs, including the molecular principles behind cargo recognition, remains elusive due to lack of tools to monitor in vitro turnover Pt(II)‐translocation events with transporters reconstituted into membrane‐mimetic systems. Here, we developed supramolecular mercaptosuccinic acid‐capped CdTe core‐type quantum dot‐encapsulated proteoliposome assemblies (MSA‐CdTe QD PLs) to demonstrate real‐time transporter‐mediated turnover translocation of Pt(II)‐complexes by Cu(I) P‐type ATPases. We coupled Pt(II)‐complex‐stimulated ATPase activity assays on the purified E. coli Cu(I)‐pump CopA with reconstitution into proteoliposomes and real‐time transport assays utilizing fluorescence detector probes (MSA‐CdTe QDs, pyranine, and oxonol VI) responsive to substrate, pH, and membrane potential, to demonstrate that Cu(I)‐pumps are electrogenic Pt(II)‐drug uniporters. Cu(I)‐pumps efficiently translocate aquated Pt(II)‐complexes with cis configuration (like cisplatin and carboplatin), but not transplatin, emphasizing how stereochemistry influences the Pt(II) transport properties. Additionally, the nature and kinetic lability of the carrier and leaving ligands were demonstrated to modulate the transport activity. Overall, MSA‐CdTe QD proteoliposome assemblies establish an extendable experimental platform to discover the Pt(II) transport properties of novel transporter classes.