FIG. 4.

Effects of gln3, gat1, and gcn4 null mutations on β-Gal activity in 5′ deletions of the GLT1 promoter. Mutant strains CLA101 (gln3Δ), CLA102 (gat1Δ), and CLA100 (gcn4Δ) harboring plasmids pLOU1, pLOU4, pLOU13, pLOU16, and pLOU17 (lines 1, 4, 13, 16, and 17) were grown on 0.2% ammonium sulfate as the nitrogen source, and β-Gal activity was determined. The reported β-Gal activities are averages of values obtained in three independent experiments. GLT1 promoter regions are represented as in Fig. 3. Variations were <15%.