A new member of the yeast amino acid (aa) permease gene family has been cloned, mapped and sequenced. The sequence of the PAP1 (putative aa permease 1) gene contains an open reading frame of 566 aa corresponding to a polypeptide with a calculated M(r) of 62,704. Its hydropathy profile suggests the presence of 13 membrane-spanning regions and a charged N-terminal domain. It does not resemble hydrophobic signal sequences found in secreted proteins. Hence, PAP1 encodes a protein with characteristics typical of integral membrane proteins translocating ligands across cellular membranes. Sequence comparisons indicate strong homology to the five known aa permeases of Saccharomyces cerevisiae and to an aa transporter in Trichoderma harzianum. Primer extension analysis revealed one major and one minor transcription start point located 121 and 125 nucleotides upstream from the ATG start codon, corresponding to a 2.1-kb transcript. PAP1 was mapped in a contig of three known (DBF4, TPI and HEM12), but so far unlinked, genes on chromosome IV.