Fig. 2.

Enhanced expression of thr and ilv operons in yeaZ(Ts), ygjD(Ts), and yjeE(Ts) mutant strains. β-Galactosidase activity was measured in temperature-sensitive mutants and their isogenic strains in which the thrA and ilvG upstream regions containing the promoter-leader peptide coding regions were inserted into the chromosomal lac operon to generate thrA′-lacZ and ilvG′-lacZ gene fusions, respectively. The fusion junctions are the initiation codons of the genes. See Materials and Methods and Fig. S5 to S7 in the supplemental material for details. (A) thrA ygjD(Ts). (B) thrA yjeE(Ts). (C) thrA yeaZ(Ts). (D) ilvG ygjD(Ts). β-Galactosidase activity in the ygjD(Ts) mutant and the parental strains carrying a thrL′-lacZ gene fusion (E) or a thrA′-lacZ terminator deletion mutant gene fusion (F). The amino acid sequences of the leader peptides of the thr and ilv operons (G). The codons for Thr, Ile, and Val are underlined, and the ANN codons are in bold font. Cells were grown overnight in Antibiotic Medium 3 and subcultured in fresh medium at a dilution of 1:100 at 30°C. Cells were incubated for 4 h, and 5 ml of the culture was used for the β-galactosidase assay. Cells were also incubated at 42°C for 2 h and assayed.