Gal3p and Gal1p interact with the transcriptional repressor Gal80p to form a complex of 1:1 stoichiometry

Biochem J. 2002 May 1;363(Pt 3):515-20. doi: 10.1042/0264-6021:3630515.


The genes encoding the enzymes required for galactose metabolism in Saccharomyces cerevisiae are controlled at the level of transcription by a genetic switch consisting of three proteins: a transcriptional activator, Gal4p; a transcriptional repressor, Gal80p; and a ligand sensor, Gal3p. The switch is turned on in the presence of two small molecule ligands, galactose and ATP. Gal3p shows a high degree of sequence identity with Gal1p, the yeast galactokinase. We have mapped the interaction between Gal80p and Gal3p, which only occurs in the presence of both ligands, using protease protection experiments and have shown that this involves amino acid residue 331 of Gal80p. Gel-filtration experiments indicate that Gal3p, or the galactokinase Gal1p, interact directly with Gal80p to form a complex with 1:1 stoichiometry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Gel
  • DNA-Binding Proteins
  • Fungal Proteins / metabolism*
  • Galactokinase / metabolism
  • Gene Expression Regulation, Fungal
  • Kinetics
  • Repressor Proteins*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Factors / metabolism*


  • DNA-Binding Proteins
  • Fungal Proteins
  • GAL4 protein, S cerevisiae
  • GAL80 protein, S cerevisiae
  • Gal3 protein, S cerevisiae
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Galactokinase