title: RAG4 gene encodes a glucose sensor in Kluyveromyces lactis.
abstract: The rag4 mutant of Kluyveromyces lactis was previously isolated as a fermentation-deficient mutant, in which transcription of the major glucose transporter gene RAG1 was affected. The wild-type RAG4 was cloned by complementation of the rag4 mutation and found to encode a protein homologous to Snf3 and Rgt2 of Saccharomyces cerevisiae. These two proteins are thought to be sensors of low and high concentrations of glucose, respectively. Rag4, like Snf3 and Rgt2, is predicted to have the transmembrane structure of sugar transporter family proteins as well as a long C-terminal cytoplasmic tail possessing a characteristic 25-amino-acid sequence. Rag4 may therefore be expected to have a glucose-sensing function. However, the rag4 mutation was fully complemented by one copy of either SNF3 or RGT2. Since K. lactis appears to have no other genes of the SNF3/RGT2 type, we suggest that Rag4 of K. lactis may have a dual function of signaling high and low concentrations of glucose. In rag4 mutants, glucose repression of several inducible enzymes is abolished.
authors.affiliation: Unité Microbiologie et Génétique, Université Claude Bernard, 43, Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cédex, France.
authors.forename: S
authors.initials: S
authors.lastname: Betina
authors.forename: P
authors.initials: P
authors.lastname: Goffrini
authors.forename: I
authors.initials: I
authors.lastname: Ferrero
authors.forename: M
authors.initials: M
authors.lastname: Wésolowski-Louvel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001692:Biological Transport; D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D003001:Cloning, Molecular; D005656:Fungal Proteins; D017353:Gene Deletion; D005947:Glucose / Q000378:metabolism* / Q000493:pharmacokinetics; D007716:Kluyveromyces / Q000235:genetics* / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics; D008957:Models, Genetic; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; C435343:RAG4 protein, Kluyveromyces; C112512:RGT2 protein, S cerevisiae; C104463:SNF3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D005947:Glucose