A comparative analysis reveals electrogenic properties of PfCRT and pendrin.

Ion translocation is an essential process in all living cells. Most traditional approaches studying ion-translocating systems have employed cellular systems replete with native proteins that potentially interfere with the functional assessment of the protein of interest. The reconstitution of purified functional target proteins into proteoliposomes (PLs), artificial membrane systems of defined lipid composition, allows for their characterization without these intricacies. Targeting three distinct proteins, NhaA, pendrin, and the Plasmodium falciparum chloroquine resistance transporter (PfCRT), upon their reconstitution into PLs with a combined array of experimental approaches centered around solid-supported membrane electrophysiology, we show the advantage of the PL study system over cell-based approaches to assess protein-specific functional features. Using NhaA, the well-characterized archetype of Na+/H+ antiporters (exchangers), as a molecular ruler, our studies reveal that pendrin, a clinically relevant anion transporter in the thyroid, ear, kidney, and lungs, catalyzes the electrogenic exchange of its transported anions, opposing a long-standing dogma of the electroneutral activity of pendrin. We also provide direct evidence that PfCRT-a key contributor in multidrug resistance that thwarts efforts to combat malaria-mediates H+-coupled drug transport.