FIGURE 2: Functional analysis of triple Ala mutations in TMS11 and TMS12. (A) Left panel: Growth tests of control strains and strains expressing GFP-tagged mutant FurE versions with triple alanine substitutions that cover the entire length of TMS11 and TMS12. WT is a standard A. nidulans wild-type strain. Δ7 is the negative control strain lacking all major nucleobase transporter and not expressing FurE. FurE is the positive control strain, which is a Δ7 strain functionally expressing FurE via the gpdA promoter. All mutant strains are isogenic to the positive control strain, also express-ing FurE versions from the gpdA promoter. Mutants are named by the number of residues substituted by Ala. Growth tests were performed on minimal media (MM) supplemented with ammonium (NH₄), uric acid (UA), allantoin (ALL) as nitrogen sources or on MM containing NO₃ and the toxic analogue 5-fluorouracil (5FU). Middle panel: Epifluorescence microscopy images of the same control and mutant strains. Scale bar is 5 μM. Right panel: PM/cytosol GFP fluorescence intensity ratios. 95% confidence intervals are pre-sented. For details see methods. (B) Ra-diolabeled uracil uptake rates, expressed as % of wt FurE rate, of strains expressing triple alanine substituted versions. For details see Materials and Methods.