“…proline, the amino acid uptake is high (Blinder et al, 1996;Courchesne et al, 1983). In S. cerevisiae, at least five proteins (Ure2p, Dal80p, Gln3p, Nil1p and Nil2p) function co-ordinately to control the transcription of GAP1 (Blinder et al, 1996;Cunningham et al, 1993;Rowen et al, 1997;Stanbrough et al, 1995). The nitrogendependent regulation of GAP1 is complex, occurring not only at the level of GAP1 transcription but also through Gap1p sorting and degradation by ubiquitin-triggered internalization (Springael et al, 1998).…”