Measurement of Energy-dependent Rhodamine 6G Efflux in Yeast Species

Rhodamine 6G is a highly fluorescent dye often used to determine the transport activity of yeast membrane efflux pumps. The ATP-binding cassette transporter KlPdr5p confers resistance to several unrelated drugs in Kluyveromyces lactis. KlPdr5p also extrudes rhodamine 6G (R6G) from intact yeast cells in an energy-dependent manner. Incubation of yeast cells in the presence of 2-deoxy-D-glucose (inhibitor of glycolysis) and R6G (mitochondrial ATPase inhibitor) leads to marked depletion of intracellular ATP pool ( Kolaczkowski et al., 1996 ). An active KlPdr5p mediated extrusion of R6G from intact yeast cells can be followed by direct measurement of the fluorescence of extruded R6G in the assay buffer.