Fig. 6. Strains lacking ARL1 do not have an apparent H⁺ efflux defect. PSY316 (ARL1; squares) and MA03 (arl1; circles) were treated as described in Materials and Methods. Measurements made in the presence of 25 mM KCl are open symbols and without KCl are closed symbols. Proton efflux was determined by measuring the change in pH after initiating the reaction with glucose. This experiment was repeated three times with similar results.