Figure 3.

Q8 deficiency impairs the activities of E. coli transporters ProP and LacY. E. coli strains WG709 (ubiG⁺, closed circles) and WG1542 (ΔubiG785::kan, open circles) were cultivated in NaCl-free MOPS medium, initial rates of proline (A) and lactose (B) uptake were determined, and data were analyzed as described under “Experimental procedures.” Assay medium osmolalities were adjusted with NaCl at concentrations in the range 0–0.15 m. Means ± S.E. (error bars) of triplicate measurements from one of two replicate experiments are shown. The osmotic activation of ProP in the ubiG⁻ E. coli strain is shown in the inset to A. The regression lines are shown in the figure, and the osmolality response parameters for the individual experiments are shown in Table S1.