Figure 4.

The effect of tetracaine on OpuA activity. (A) Uptake of [¹⁴C]glycine betaine (final concentration of 80 μM) was assayed in 90 mM KP_i, pH 7.0, with (■) or without (●) 400 mM KCl (680 mosmol/kg). Both curves were fitted with the double exponential decay function f(x) = a⋅exp(−b⋅x) + c⋅exp(−d⋅x). Inset shows the data on a logarithmic scale. (B) Uptake of [¹⁴C]glycine betaine (final concentration of 80 μM) was assayed in 90 mM KP_i, pH 7.0, with (■) or without (●) 1 mM tetracaine. The osmolality of the medium was varied with KCl. ▵ Osmolality has the same meaning as in the legend to Fig. 3.