GAL3/YDR009W Summary Help

Standard Name GAL3 1
Systematic Name YDR009W
Feature Type ORF, Verified
Description Transcriptional regulator; involved in activation of the GAL genes in response to galactose; forms a complex with Gal80p to relieve Gal80p inhibition of Gal4p; binds galactose and ATP but does not have galactokinase activity; GAL3 has a paralog, GAL1, that arose from the whole genome duplication (2, 3, 4, 5 and see Summary Paragraph)
Name Description GALactose metabolism
Chromosomal Location
ChrIV:463434 to 464996 | ORF Map | GBrowse
Genetic position: 1 cM
Gene Ontology Annotations All GAL3 GO evidence and references
  View Computational GO annotations for GAL3
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 2 genes
Classical genetics
Large-scale survey
83 total interaction(s) for 47 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 1
  • Affinity Capture-Western: 4
  • Co-crystal Structure: 2
  • Co-purification: 1
  • FRET: 1
  • PCA: 2
  • Reconstituted Complex: 4
  • Two-hybrid: 3

Genetic Interactions
  • Dosage Rescue: 4
  • Negative Genetic: 37
  • Phenotypic Enhancement: 13
  • Phenotypic Suppression: 4
  • Positive Genetic: 4
  • Synthetic Growth Defect: 1
  • Synthetic Rescue: 2

Expression Summary
Length (a.a.) 520
Molecular Weight (Da) 58,129
Isoelectric Point (pI) 6.94
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIV:463434 to 464996 | ORF Map | GBrowse
Genetic position: 1 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1563 463434..464996 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000002416

GAL3 encodes a transcriptional regulator involved in gene activation in response to galactose (6). Among the genes that, in conjunction with Gal4p and Gal80p, are regulated by Gal3p are the GAL metabolic genes GAL1, GAL10, GAL2, and GAL7 (reviewed in 7). In the presence of galactose and ATP, Gal3p binds to the transcriptional repressor Gal80p, which relieves inhibition of the Gal4p transcription factor and results in GAL gene expression (4, 8). GAL3 transcription is also regulated by the Gal3p/Gal80p/Gal4p feedback mechanism that regulates the other GAL genes. However, unlike expression of the GAL structural genes, which is tightly controlled because of the presence of multiple upstream activation sites (UAS-GALs) in their promoters, GAL3 has high basal levels of transcription due to the presence of only a single UAS-GAL in its promoter (9).

GAL3 is thought to have arisen from GAL1 as a result of the S. cerevisiae whole genome duplication and the two proteins share 90% amino acid similarity (10). Insertion of just two amino acids (a serine and an alanine) directly after amino acid 164 is able to confer galactokinase activity on Gal3p. Null mutants of gal3 exhibit at 3-5 day lag in transcriptional induction (as opposed to several minutes in wild-type cells), a phenotype which can be complemented by GAL1 overexpression (11).

Last updated: 2013-05-23 Contact SGD

References cited on this page View Complete Literature Guide for GAL3
1) Tsuyumu S and Adams BG  (1973) Population analysis of the deinduction kinetics of galactose long-term adaptation mutants of yeast. Proc Natl Acad Sci U S A 70(3):919-23
2) Platt A and Reece RJ  (1998) The yeast galactose genetic switch is mediated by the formation of a Gal4p-Gal80p-Gal3p complex. EMBO J 17(14):4086-91
3) Bhat PJ and Murthy TV  (2001) Transcriptional control of the GAL/MEL regulon of yeast Saccharomyces cerevisiae: mechanism of galactose-mediated signal transduction. Mol Microbiol 40(5):1059-66
4) Timson DJ, et al.  (2002) Gal3p and Gal1p interact with the transcriptional repressor Gal80p to form a complex of 1:1 stoichiometry. Biochem J 363(Pt 3):515-20
5) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
6) Torchia TE and Hopper JE  (1986) Genetic and molecular analysis of the GAL3 gene in the expression of the galactose/melibiose regulon of Saccharomyces cerevisiae. Genetics 113(2):229-46
7) Lohr D, et al.  (1995) Transcriptional regulation in the yeast GAL gene family: a complex genetic network. FASEB J 9(9):777-87
8) Peng G and Hopper JE  (2002) Gene activation by interaction of an inhibitor with a cytoplasmic signaling protein. Proc Natl Acad Sci U S A 99(13):8548-53
9) Melcher K and Xu HE  (2001) Gal80-Gal80 interaction on adjacent Gal4p binding sites is required for complete GAL gene repression. EMBO J 20(4):841-51
10) Platt A, et al.  (2000) The insertion of two amino acids into a transcriptional inducer converts it into a galactokinase. Proc Natl Acad Sci U S A 97(7):3154-9
11) Bhat PJ, et al.  (1990) Analysis of the GAL3 signal transduction pathway activating GAL4 protein-dependent transcription in Saccharomyces cerevisiae. Genetics 125(2):281-91