FIG. 2.
Inhibition of Uhp induction by addition of inorganic phosphate. (A) RK5115 cells in MOPS minimal medium with 30 mM succinate were induced with 5 μM glucose 6-phosphate at time zero. Phosphate was added at 12.5 min (arrow), and samples were analyzed as described in Materials and Methods. Symbols: ♦, 0 mM Pi; ⋄, 2 mM Pi; ∗, 5 mM Pi; ×, 10 mM Pi. (B) Rates (VUhp) at various glucose 6-phosphate concentrations were obtained by determining the slope of the linear trendlines of β-galactosidase activity versus time, as in A, between 15 and 42.5 min for each phosphate concentration tested. Glucose 6-phosphate concentrations: ▴, 1 μM; □, 2.5 μM; ▪, 5 μM; ○, 10 μM; •, 20 μM. [Pi]0, intersection of the line representing VUhp with the horizontal axis (VUhp = 0).