In a strain disrupted in GAP1, additional disruption of AGP1 greatly reduced growth of yeast on medium containing 1.0 mM phenylalanine as the sole nitrogen source .
In the present study, we focused on the participation of GAP1 , BAP2 [15,17], and AGP1 [13,18] in L-phenylalanine transport.
 employed overexpression and deletion to show that BAP2, AGP1, BAP3, and TAT2 could be involved in phenylalanine uptake.
In order to study the physiological functions of GAP1, BAP2, and AGP1 in L-phenylalanine transport, we examined the kinetics, substrate specificity, and regulation of these systems, employing isogenic haploid strains with the respective genes disrupted individually and in combination.
The Saccharomyces cerevisiae strains used in this study are all isogenic with the "wild type" parental strain Y294, MAT [alpha] ura3-52 leu 2-3,112 his3-[DELTA]1 trp1-289  except for the mutations mentioned; Y294[DELTA]bap2 with bap2::URA3; Y294[DELTA]gap1 with gap1::LEU2; Y294d[DELTA]bap2[DELTA]gap1 with bap2::URA3 and gap1::LEU2; ; Y294 [DELTA]agp1 with agp1::URA3, and Y294[DELTA]agp1[DELTA]gap1 with agp1::HIS3 and gap1::LEU2.
Disruption of AGP1 in a gap1 Strain Reduces Growth on Branched-Chain and Aromatic Amino Acids.
This pathway senses external amino acids and transmits a transcriptional activation impulse to multiple AAP genes, including BAP2 and AGP1 [12,13, 21].
[4, 25] used 0.15 mM leucine to activate transcription of several additional permease genes, including AGP1, via the SPS signalling pathway.
Disruption of BAP2 or AGP1 Leads to a Reduced Uptake of L-Phenylalanine.
The residual uptake is not due to Agp1p, since deletion of AGP1 has almost no negative, effect irrespective of phenylalanine concentration (Figures 1(a) and 1(b)).