THE PERMEASE HOMOLOG SSY1P CONTROLS THE EXPRESSION OF AMINO-ACID AND PEPTIDE TRANSPORTER GENES IN SACCHAROMYCES-CEREVISIAE

Amino acid transporters of the yeast plasma membrane (permeases) belon g to a family of integral membrane proteins with pronounced structural similarity. We present evidence that a member of this family, encoded by the open reading frame (ORF) YDR160w (SSY1), is required for the e xpression of a set of transporter genes, Thus, deletion of the SSY1 ge ne causes loss of leucine-inducible transcription of the amino acid pe rmease genes BAP2, TATI and BAP3 (ORF YDR046c) and the peptide transpo rter, PTR2. D-leucine can generate the signal without entering the cel l. We propose that Ssy1p is situated in the plasma membrane and is inv olved in sensing leucine in the medium.