Fig. 4. The insensitivity of glutamate repression of CIT2-lacZ reporter gene expression in lst8-5 mutant cells is not the result of a defect in glutamate uptake. (A) Lst8-5 and lst8-1 mutants are largely insensitive to glutamate repression of CIT2-lacZ reporter gene expression. Wild-type (PSY142), lst8-1 and lst8-5 mutant strains with an integrated copy of CIT2-lacZ reporter gene were grown in YNB5%D medium with or without 0.2% glutamate. Whole-cell extracts were prepared and β-galactosidase activities were determined as described in Materials and methods. (B) Glutamate uptake in wild-type and lst8-5 mutant cells. Wild-type (PSY142) and lst8-5 mutant strains were grown in YNBD medium and glutamate uptake was assayed as described in Materials and methods. Glutamate was present at a final concentration of 0.01%. (C) Glutamate uptake into wild-type and gap1Δ dip5Δ mutant strains. Wild-type (S288C) and a gap1Δ dip5Δ derivative strain were grown in YNBD medium, and the glutamate uptake assay was carried out as described in (B). (D) CIT2-lacZ reporter gene expression is still repressed by glutamate in gap1Δ dip5Δ mutant cells. Wild-type (S288C) and a gap1Δ dip5Δ mutant derivative strain were grown in YNB5%D medium with or without glutamate as indicated. Whole-cell extracts were prepared and β-galactosidase activities were determined as described in Materials and methods.