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The Gal3p transducer of the GAL regulon interacts with the Gal80p repressor in its ligand-induced closed conformation.

A wealth of genetic information and some biochemical analysis have made the GAL regulon of the yeast Saccharomyces cerevisiae a classic model system for studying transcriptional activation in eukaryotes. Galactose induces this transcriptional switch, which is regulated by three proteins: the transcriptional activator Gal4p, bound to DNA; the repressor Gal80p; and the transducer Gal3p. We showed previously that NADP appears to act as a trigger to kick the repressor off the activator. Sustained activation involves a complex of the transducer Gal3p and Gal80p mediated by galactose and ATP. We solved the crystal structure of the complex of Gal3p-Gal80p with α-D-galactose and ATP to 2.1 Å resolution. The interaction between the proteins occurs only when Gal3p is in a "closed" state induced by ligand binding. The structure of the complex provides a rationale for the phenotypes of several well-known Gal80p and Gal3p mutants as well as the lack of galactokinase activity of Gal3p.

Pubmed ID: 22302941


  • Lavy T
  • Kumar PR
  • He H
  • Joshua-Tor L


Genes & development

Publication Data

February 1, 2012

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM074075
  • Agency: NCI NIH HHS, Id: P30 CA045508
  • Agency: Howard Hughes Medical Institute, Id:

Mesh Terms

  • Adenosine Triphosphate
  • Binding Sites
  • Galactokinase
  • Galactose
  • Humans
  • Hydrogen Bonding
  • Ligands
  • Models, Molecular
  • Mutation
  • Protein Binding
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Regulon
  • Repressor Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Transcriptional Activation