STE18/YJR086W Summary Help

Standard Name STE18 1
Systematic Name YJR086W
Feature Type ORF, Verified
Description G protein gamma subunit; forms a dimer with Ste4p to activate the mating signaling pathway, forms a heterotrimer with Gpa1p and Ste4p to dampen signaling; C-terminus is palmitoylated and farnesylated, which are required for normal signaling (2, 3 and see Summary Paragraph)
Name Description STErile
Chromosomal Location
ChrX:586068 to 586400 | ORF Map | GBrowse
Genetic position: 59 cM
Gene Ontology Annotations All STE18 GO evidence and references
  View Computational GO annotations for STE18
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 2 genes
Classical genetics
dominant negative
30 total interaction(s) for 12 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 2
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 5
  • FRET: 1
  • PCA: 1
  • Two-hybrid: 7

Genetic Interactions
  • Dosage Rescue: 3
  • Phenotypic Enhancement: 4
  • Phenotypic Suppression: 2
  • Synthetic Rescue: 3

Expression Summary
Length (a.a.) 110
Molecular Weight (Da) 12,625
Isoelectric Point (pI) 10.35
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrX:586068 to 586400 | ORF Map | GBrowse
Genetic position: 59 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..333 586068..586400 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 SGDIDS000003846

STE18 encodes the gamma subunit of the heterotrimeric G-protein complex involved in the mating pathway (2). Yeast respond to mating pheromone by transducing the pheromone signal through a well-studied mitogen-activated protein kinase (MAPK) cascade (reviewed in 4, 5). The first step in the mating pathway is the binding of mating pheromone to its receptor; the pheromone receptors are encoded by STE2 in MATa cells and STE3 in MATalpha cells (6, 7). These receptors transmit their signals through a heterotrimeric G protein consisting of Gpa1p, the G-alpha subunit, Ste4p, the beta subunit, and Ste18p, the gamma subunit (8, 5, 4). After binding pheromone, the pheromone receptor undergoes a conformational change and there is an exchange of GDP for GTP on Gpa1p. In its GTP-bound form, Gpa1p has less affinity for the Ste4p-Ste18p (beta-gamma) complex, and the latter is released and able to activate downstream components of the pheromone response pathway (8, 5, 4). The beta-gamma complex binds to both the scaffolding protein Ste5p, facilitating recruitment of Ste5p and its associated kinases (Ste11p, Ste7p, and Fus3p) to the plasma membrane, and to the PAK kinase Ste20p (9, 10, 11, 12). The Ste4p-Ste18p dimer also interacts with a complex of Far1p and Cdc24p; in total, these interactions induce expression of genes involved in mating, polarization of cell growth, and ultimately cell and nuclear fusion (reviewed in 13). Cells lacking Ste18p are unable to mate (2) and do not localize Ste4p to the plasma membrane (14). Membrane association of the dimer is required for activation of the downstream pathway (10) and appears to be stabilized by dual lipid modification of Ste18p (farnesylation and palmitoylation) (3, 15).

Last updated: 2007-06-01 Contact SGD

References cited on this page View Complete Literature Guide for STE18
1) Whiteway M, et al.  (1988) Expression of MF alpha 1 in MATa cells supersensitive to alpha-factor leads to self-arrest. Mol Gen Genet 214(1):85-8
2) Whiteway M, et al.  (1989) The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein. Cell 56(3):467-77
3) Hirschman JE and Jenness DD  (1999) Dual lipid modification of the yeast ggamma subunit Ste18p determines membrane localization of Gbetagamma. Mol Cell Biol 19(11):7705-11
4) Herskowitz I  (1995) MAP kinase pathways in yeast: for mating and more. Cell 80(2):187-97
5) Konopka JB and Fields S  (1992) The pheromone signal pathway in Saccharomyces cerevisiae. Antonie Van Leeuwenhoek 62(1-2):95-108
6) Burkholder AC and Hartwell LH  (1985) The yeast alpha-factor receptor: structural properties deduced from the sequence of the STE2 gene. Nucleic Acids Res 13(23):8463-75
7) Hagen DC, et al.  (1986) Evidence the yeast STE3 gene encodes a receptor for the peptide pheromone a factor: gene sequence and implications for the structure of the presumed receptor. Proc Natl Acad Sci U S A 83(5):1418-22
8) Blumer KJ and Thorner J  (1990) Beta and gamma subunits of a yeast guanine nucleotide-binding protein are not essential for membrane association of the alpha subunit but are required for receptor coupling. Proc Natl Acad Sci U S A 87(11):4363-7
9) Mahanty SK, et al.  (1999) Nuclear shuttling of yeast scaffold Ste5 is required for its recruitment to the plasma membrane and activation of the mating MAPK cascade. Cell 98(4):501-12
10) Pryciak PM and Huntress FA  (1998) Membrane recruitment of the kinase cascade scaffold protein Ste5 by the Gbetagamma complex underlies activation of the yeast pheromone response pathway. Genes Dev 12(17):2684-97
11) Dowell SJ, et al.  (1998) Mapping of a yeast G protein betagamma signaling interaction. Genetics 150(4):1407-17
12) Leeuw T, et al.  (1998) Interaction of a G-protein beta-subunit with a conserved sequence in Ste20/PAK family protein kinases. Nature 391(6663):191-5
13) Bardwell L  (2005) A walk-through of the yeast mating pheromone response pathway. Peptides 26(2):339-50
14) Hirschman JE, et al.  (1997) The G beta gamma complex of the yeast pheromone response pathway. Subcellular fractionation and protein-protein interactions. J Biol Chem 272(1):240-8
15) Manahan CL, et al.  (2000) Dual lipid modification motifs in G(alpha) and G(gamma) subunits are required for full activity of the pheromone response pathway in Saccharomyces cerevisiae. Mol Biol Cell 11(3):957-68