FIGURE 2.

Transport activity of double Cys mutants in RSO membrane vesicles. The double Cys mutants in the “Cys-less” background were expressed in E. coli T184 as described under “Experimental Procedures.” Active transport was assayed in the presence of 20 mm ascorbate and 0.2 mm phenazine methosulfate under oxygen with [1-¹⁴C]lactose (2.5 mCi/mmol) at a final concentration of 0.4 mm at room temperature for 5 min, measurements were carried out in triplicate. Results are expressed as a percentage of activity in the Cys-less mutant.