Membrane Transport of Rhodamine 6G by the reconstituted multidrug resistance–ABC transporter Pdr5 in Horizontal Lipid Bilayer

Pdr5 is the most abundant ABC transporter in Saccharomyces cerevisiae and plays a key role in the pleiotropic drug resistance (PDR) network, actively preventing the sustained entry of a wide range of structurally diverse compounds into the cell. This transporter has been extensively studied in vivo , in plasma membrane vesicles, and more recently, after reconstitution into artificial membranes, making it a widely used model system for ABC transporter research. Recent structural studies of Pdr5 have provided new insights into its architecture and function. However, the precise molecular mechanisms underlying Pdr5-mediated membrane transport remain largely unresolved. In this study, we investigate the interaction of reconstituted Pdr5 in an artificial freestanding horizontal lipid bilayer system with Rhodamine 6G (R6G), a well-known Pdr5 substrate. We show that functionally reconstituted Pdr5 actively transports the R6G ⁺ cation across the membrane in an ATP-dependent manner, moving it from one bulk phase to the other.