title: BAP2, a gene encoding a permease for branched-chain amino acids in Saccharomyces cerevisiae.
abstract: To select the gene coding for an isoleucine permease, an isoleucine dependent strain (ilv1 cha1) was transformed with a yeast genomic multicopy library, and colonies growing at a low isoleucine concentration were selected. Partial sequencing of the responsible plasmid insert revealed the presence of a previously sequenced 609 codon open reading frame of chromosome II with homology to known permeases. Deletion, extra dosage and C-terminal truncation of this gene were constructed in a strain lacking the general amino acid permease, and amino acid uptake was measured during growth in synthetic complete medium. The following observations prompted us to name the gene BAP2 (branched-chain amino acid permease). Deletion of BAP2 reduced uptake of leucine, isoleucine and valine by 25-50%, while the uptake of 8 other L-alpha-amino acids was unaltered or slightly increased. Introduction of BAP2 on a centromere-based vector, leading to a gene dosage of two or slightly more, caused a 50% increase in leucine uptake and a smaller increase for isoleucine and valine. However, when the 29 C-terminal codons of the plasmid-borne copy of BAP2 were substituted, the cells more than doubled the uptake of leucine, isoleucine and valine, while no or little increase in uptake was observed for the other 8 amino acids.
mesh_terms: D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems; D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D017353:Gene Deletion; D005800:Genes, Fungal; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D026905:Amino Acid Transport Systems; D000597:Amino Acids, Branched-Chain; C097094:BAP2 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins