GAL2/YLR081W Summary Help

Standard Name GAL2 1
Systematic Name YLR081W
Feature Type ORF, Verified
Description Galactose permease; required for utilization of galactose; also able to transport glucose (2, 3, 4 and see Summary Paragraph)
Name Description GALactose metabolism
Chromosomal Location
ChrXII:290212 to 291936 | ORF Map | GBrowse
Genetic position: 44 cM
Gene Ontology Annotations All GAL2 GO evidence and references
  View Computational GO annotations for GAL2
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 9 genes
Classical genetics
Large-scale survey
47 total interaction(s) for 40 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 2
  • Two-hybrid: 1

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 26
  • Positive Genetic: 7
  • Synthetic Growth Defect: 5
  • Synthetic Rescue: 5

Expression Summary
Length (a.a.) 574
Molecular Weight (Da) 63,625
Isoelectric Point (pI) 7.21
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXII:290212 to 291936 | ORF Map | GBrowse
Genetic position: 44 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1725 290212..291936 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) | TCDB | UniProtKB
Primary SGDIDS000004071

GAL2 encodes a high affinity galactose permease that is also able to transport glucose (5, 4). Gal2p is an integral plasma membrane protein belonging to a superfamily of sugar transporters that are predicted to contain 12 transmembrane domains separated by charged residues (6). Structurally and functionally similar sugar transporters have been identified in bacteria, rat, and humans (6, 7). Gal2p is integral to the process of galactose catabolism, and loss of its permease activity renders cells unable to utilize galactose as a sole carbon source (1).

All the galactose structural genes (GAL1, GAL10, GAL7, GAL2) are coordinately regulated at the level of transcription in response to galactose by Gal4p, Gal80p, and Gal3p (8, 9, and reviewed in 10). Regardless of carbon source, the Gal4p transcriptional activator is bound as a dimer to upstream activation sites found in the promoters of the GAL genes. In the presence of galactose, Gal3p sequesters the transcriptional repressor Gal80p in the cytoplasm, thereby relieving inhibition of Gal4p and resulting in GAL gene expression (11). In the absence of galactose, Gal80p remains bound as a dimer, to Gal4p, preventing Gal4p from recruiting other factors of the Pol II transcription machinery (reviewed in 10).

When cells are grown on glucose, GAL2 is negatively regulated by catabolite repression at both the levels of transcription and protein degradation. Downregulation of GAL2 expression is mediated by Sip1p, a subunit of the Snf1p kinase complex (12). Grr1p-dependent protein degradation of Gal2p occurs through ubiquitination at several lysine residues, followed by endocytosis and vacuolar proteolysis (13, 14, 15).

Last updated: 2006-10-12 Contact SGD

References cited on this page View Complete Literature Guide for GAL2
1) Douglas HC and CONDIE F  (1954) The genetic control of galactose utilization in Saccharomyces. J Bacteriol 68(6):662-70
2) Rodriguez C and Flores C  (2000) Mutations in GAL2 or GAL4 alleviate catabolite repression produced by galactose in Saccharomyces cerevisiae. Enzyme Microb Technol 26(9-10):748-755
3) Kasahara T and Kasahara M  (2000) Three aromatic amino acid residues critical for galactose transport in yeast Gal2 transporter. J Biol Chem 275(6):4422-8
4) Maier A, et al.  (2002) Characterisation of glucose transport in Saccharomyces cerevisiae with plasma membrane vesicles (countertransport) and intact cells (initial uptake) with single Hxt1, Hxt2, Hxt3, Hxt4, Hxt6, Hxt7 or Gal2 transporters. FEMS Yeast Res 2(4):539-50
5) Tschopp JF, et al.  (1986) GAL2 codes for a membrane-bound subunit of the galactose permease in Saccharomyces cerevisiae. J Bacteriol 166(1):313-8
6) Nehlin JO, et al.  (1989) Yeast galactose permease is related to yeast and mammalian glucose transporters. Gene 85(2):313-9
7) Kasahara T and Kasahara M  (1998) Tryptophan 388 in putative transmembrane segment 10 of the rat glucose transporter Glut1 is essential for glucose transport. J Biol Chem 273(44):29113-7
8) De Robichon-Szulmajster H  (1958) Induction of enzymes of the galactose pathway in mutants of Saccharomyces cerevisiae. Science 127(3288):28-9
9) 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
10) Lohr D, et al.  (1995) Transcriptional regulation in the yeast GAL gene family: a complex genetic network. FASEB J 9(9):777-87
11) 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
12) Mylin LM, et al.  (1994) SIP1 is a catabolite repression-specific negative regulator of GAL gene expression. Genetics 137(3):689-700
13) Horak J and Wolf DH  (1997) Catabolite inactivation of the galactose transporter in the yeast Saccharomyces cerevisiae: ubiquitination, endocytosis, and degradation in the vacuole. J Bacteriol 179(5):1541-9
14) Horak J and Wolf DH  (2001) Glucose-induced monoubiquitination of the Saccharomyces cerevisiae galactose transporter is sufficient to signal its internalization. J Bacteriol 183(10):3083-8
15) Horak J and Wolf DH  (2005) The ubiquitin ligase SCF(Grr1) is required for Gal2p degradation in the yeast Saccharomyces cerevisiae. Biochem Biophys Res Commun 335(4):1185-90