FIGURE 7.
The effect of pH on the activity and osmotic activation of parental OpuA, OpuAΔ12, and OpuAΔ12insHis. Proteoliposomes were loaded with 9 mm MgSO4, 9 mm Na2ATP plus 50 mm potassium Pi at the corresponding pH, which is equiosmolar with 70 mm potassium Pi of the outside medium. Uptake of [14C]glycine betaine by OpuA (•), OpuAΔ12 (○), and OpuAΔ12insHis (▴) in 70 mm potassium Pi and supplemented with 0 mm KCl (A), 100 mm KCl (B), and 200 mm KCl (C) is shown. Proteoliposomes were composed of 50 mol % DOPE, 12 mol % DOPC, and 38 mol % DOPG.