FIG. 6.

Phosphate exchange across the membrane of IPTG-induced E. coli cells. E. coli cells (uhpT::Tn1000) harbored either plasmid pET16b (✚), uhpC/pET16b (⧫), hptcp/pET16b (▴), or uhpT/pET16b (▪). (A) Effect of dilution on internal P_i concentration. After incubation with 100 μM ³²P_i, unlabeled P_i was added to a final concentration of 10 mM (arrow). Cells were grown in M63 medium (see Materials and Methods) and washed twice with MOPS buffer medium. (B) After incubation with 100 μM ³²P_i for 5 min and removal of external radioactivity, each suspension of IPTG-induced E. coli cells (uhpT::Tn1000) harboring plasmid hptcp/pET16b received MOPS buffer medium with or without 2 mM erythrose 4-phosphate or Glc6P.