STE5/YDR103W Summary Help

Standard Name STE5 1
Systematic Name YDR103W
Alias HMD3 2 , NUL3 3
Feature Type ORF, Verified
Description Pheromone-responsive MAPK scaffold protein; couples activation of the G-protein-coupled pheromone receptor to MAPK activation; intramolecular interaction of PH and VWA domains blocks activation of assembled signaling cascade components (Ste11p, Ste7p and Fus3p) under basal conditions; Gbeta-gamma (Ste4p-Ste18p)-dependent docking at the plasma membrane and binding of PI(4,5)P2 by the PH domain relieves autoinhibition, resulting in pheromone-dependent pathway activation (4, 5, 6, 7, 8, 9, 10, 11, 12 and see Summary Paragraph)
Name Description STErile 1
Chromosomal Location
ChrIV:658350 to 661103 | ORF Map | GBrowse
Genetic position: 63 cM
Gene Ontology Annotations All STE5 GO evidence and references
  View Computational GO annotations for STE5
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 1 genes
Classical genetics
Large-scale survey
151 total interaction(s) for 49 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 13
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 38
  • Biochemical Activity: 2
  • Co-crystal Structure: 1
  • Co-fractionation: 1
  • Co-localization: 1
  • Co-purification: 1
  • Far Western: 1
  • FRET: 7
  • PCA: 2
  • Protein-peptide: 1
  • Reconstituted Complex: 11
  • Two-hybrid: 31

Genetic Interactions
  • Dosage Rescue: 9
  • Phenotypic Enhancement: 9
  • Phenotypic Suppression: 10
  • Synthetic Lethality: 1
  • Synthetic Rescue: 10

Expression Summary
Length (a.a.) 917
Molecular Weight (Da) 102,726
Isoelectric Point (pI) 5.19
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIV:658350 to 661103 | ORF Map | GBrowse
Genetic position: 63 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..2754 658350..661103 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 SGDIDS000002510

STE5 encodes a scaffold protein that assembles the protein kinases of the pheromone-activated MAPK cascade into an active complex during mating (5, 13, reviewed in 14). Distinct regions of Ste5p interact with the MAPK Fus3p, the MAPK kinase (MAPKK) Ste7p, and the MAPKK kinase (MAPKKK) Ste11p to form the active complex (15, 6, 16).

Haploid yeast cells, which exist as either MATa or MATalpha mating types, initiate mating to form diploids through production of peptide pheromones (a factor or alpha factor). Pheromones bind to seven-transmembrane receptor proteins on cells of the opposite type: Ste2p (MATa cells) or Ste3p (MATalpha cells) (17, 18), leading to activation of the heterotrimeric G-protein composed of alpha subunit Gpa1p, beta subunit Ste4p, and gamma subunit Ste18p (19, 20, 21). Activation is mediated by exchange of GDP for GTP on the alpha subunit, causing it to dissociate from the heterotrimer. The resulting Ste4p-Ste18p dimer helps to recruit the scaffolding protein Ste5p and its associated MAP kinase cascade components, Ste11p, Ste7p, and Fus3p, to the membrane, where Ste11p is phosphorylated by the PAK kinase Ste20p (22, 23); Ste11p then phosphorylates Ste7p, which phosphorylates MAPKs Fus3p and Kss1p (24, 25). Both MAPKs phosphorylate the transcription activator Ste12p, which induces a number of mating-specific genes; in addition, Fus3p phosphorylates the cell cycle regulator Far1p, which mediates cell cycle arrest and is also involved, with Cdc24p, in polarized growth toward the mating partner (26, reviewed in 27).

The Ste5p scaffold plays two positive roles in the mating signal transduction pathway. First, it binds the components of the MAPK cascade and holds them in an active complex; second, it associates with the plasma membrane, bringing the kinases to the plasma membrane where Ste11p can be activated by the Ste20p kinase (28, 29). Membrane binding also promotes amplification of the signal, possibly by concentrating the bound kinases (30). Ste5p binds to Ste4p through the Ste5p amino terminal RING-H2 motif, which also mediates oligomerization of Ste5p (31). Oligomerization is important for proper signaling although it is not essential for mating (32, 28). Although Ste4p helps recruit Ste5p and its associated MAP kinases to the membrane, membrane attachment is not absolutely dependent on interaction with Ste4p, as shown by the isolation of ste5 mutants that permit signaling in the absence of Gbeta-gamma (33). Rather, two regions within Ste5p are required for membrane association: a pleckstrin-homology (PH) domain (residues 388-518) that is conserved among Saccharomyces species and is essential for maximal pheromone signaling, and an amphipathic alpha-helical domain in the amino terminus (residues 37-76) called the PM/NLS domain (8, 7).

In vegetative cells Ste5p shuttles between the cytoplasm and nucleus, and the kinases are bound to it in the presence or absence of pheromone (34, 6, 15). Upon pheromone stimulation, a pool of nuclear Ste5p is exported to the plasma membrane and shmoo tip, colocalizing with the Ste4p-Ste18p complex of the G protein (34, 28). Nuclear shuttling appears not to be essential for Ste5p translocation to the plasma membrane; thus it may serve as a mechanism for sequestering Ste5p to prevent inappropriate signaling (reviewed in 35).

In addition to promoting efficient propagation of the pheromone signal, Ste5p also functions to downregulate signaling (36) via a negative feedback loop. Interaction of Fus3p with Ste5p stimulates autophosphorylation of Fus3p at one of two phosphorylation sites (that are typically modified by Ste7p during signal transduction). Monophosphorylated Fus3p phosphorylates Ste5p (the proposed site is residue T287), which leads to a decrease in signaling (36).

Pheromone-induced cell cycle arrest is restricted to the G1 phase by G1 cyclin dependent protein kinases (CDKs), which phosphorylate Ste5p at a cluster of CDK sites near the PM domain (37). This phosphorylation disrupts Ste5p membrane localization and therefore signaling. Ste5p thus acts as a point of integration for response to the external pheromone signal, which causes arrest in G1, and commitment to a new cell cycle, which inhibits pheromone signaling (37).

While some other fungi contain Ste5p homologs, no obvious mammalian homologs have been identified. However, a number of proteins that function as MAPK cascade scaffolds have been identified in mammalian cells and other organisms (reviewed in 35).

Last updated: 2007-09-17 Contact SGD

References cited on this page View Complete Literature Guide for STE5
1) Liao H and Thorner J  (1980) Yeast mating pheromone alpha factor inhibits adenylate cyclase. Proc Natl Acad Sci U S A 77(4):1898-902
2) Sugimoto K, et al.  (1995) Dosage suppressors of the dominant G1 cyclin mutant CLN3-2: identification of a yeast gene encoding a putative RNA/ssDNA binding protein. Mol Gen Genet 248(6):712-8
3) Mortimer RK and Hawthorne DC  (1973) Genetic Mapping in Saccharomyces IV. Mapping of Temperature-Sensitive Genes and Use of Disomic Strains in Localizing Genes. Genetics 74(1):33-54
4) Choi KY, et al.  (1999) Characterization of Fus3 localization: active Fus3 localizes in complexes of varying size and specific activity. Mol Biol Cell 10(5):1553-68
5) Printen JA and Sprague GF Jr  (1994) Protein-protein interactions in the yeast pheromone response pathway: Ste5p interacts with all members of the MAP kinase cascade. Genetics 138(3):609-19
6) Kranz JE, et al.  (1994) The MAP kinase Fus3 associates with and phosphorylates the upstream signaling component Ste5. Genes Dev 8(3):313-27
7) Winters MJ, et al.  (2005) A membrane binding domain in the ste5 scaffold synergizes with gbetagamma binding to control localization and signaling in pheromone response. Mol Cell 20(1):21-32
8) Garrenton LS, et al.  (2006) Function of the MAPK scaffold protein, Ste5, requires a cryptic PH domain. Genes Dev 20(14):1946-58
9) Hao N, et al.  (2008) Regulation of cell signaling dynamics by the protein kinase-scaffold Ste5. Mol Cell 30(5):649-56
10) Good M, et al.  (2009) The Ste5 scaffold directs mating signaling by catalytically unlocking the Fus3 MAP kinase for activation. Cell 136(6):1085-97
11) Malleshaiah MK, et al.  (2010) The scaffold protein Ste5 directly controls a switch-like mating decision in yeast. Nature 465(7294):101-5
12) Zalatan JG, et al.  (2012) Conformational control of the Ste5 scaffold protein insulates against MAP kinase misactivation. Science 337(6099):1218-22
13) Marcus S, et al.  (1994) Complexes between STE5 and components of the pheromone-responsive mitogen-activated protein kinase module. Proc Natl Acad Sci U S A 91(16):7762-6
14) Elion EA  (2001) The Ste5p scaffold. J Cell Sci 114(Pt 22):3967-78
15) Choi KY, et al.  (1994) Ste5 tethers multiple protein kinases in the MAP kinase cascade required for mating in S. cerevisiae. Cell 78(3):499-512
16) Inouye C, et al.  (1997) Mutational analysis of STE5 in the yeast Saccharomyces cerevisiae: application of a differential interaction trap assay for examining protein-protein interactions. Genetics 147(2):479-92
17) 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
18) 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
19) 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
20) Dietzel C and Kurjan J  (1987) The yeast SCG1 gene: a G alpha-like protein implicated in the a- and alpha-factor response pathway. Cell 50(7):1001-10
21) Miyajima I, et al.  (1987) GPA1, a haploid-specific essential gene, encodes a yeast homolog of mammalian G protein which may be involved in mating factor signal transduction. Cell 50(7):1011-9
22) 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
23) Dowell SJ, et al.  (1998) Mapping of a yeast G protein betagamma signaling interaction. Genetics 150(4):1407-17
24) Neiman AM and Herskowitz I  (1994) Reconstitution of a yeast protein kinase cascade in vitro: activation of the yeast MEK homologue STE7 by STE11. Proc Natl Acad Sci U S A 91(8):3398-402
25) Ma D, et al.  (1995) Phosphorylation and localization of Kss1, a MAP kinase of the Saccharomyces cerevisiae pheromone response pathway. Mol Biol Cell 6(7):889-909
26) Elion EA, et al.  (1993) FUS3 phosphorylates multiple components of the mating signal transduction cascade: evidence for STE12 and FAR1. Mol Biol Cell 4(5):495-510
27) Bardwell L  (2005) A walk-through of the yeast mating pheromone response pathway. Peptides 26(2):339-50
28) 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
29) Drogen F, et al.  (2000) Phosphorylation of the MEKK Ste11p by the PAK-like kinase Ste20p is required for MAP kinase signaling in vivo. Curr Biol 10(11):630-9
30) Lamson RE, et al.  (2006) Dual role for membrane localization in yeast MAP kinase cascade activation and its contribution to signaling fidelity. Curr Biol 16(6):618-23
31) Inouye C, et al.  (1997) Ste5 RING-H2 domain: role in Ste4-promoted oligomerization for yeast pheromone signaling. Science 278(5335):103-6
32) Yablonski D, et al.  (1996) Dimerization of Ste5, a mitogen-activated protein kinase cascade scaffold protein, is required for signal transduction. Proc Natl Acad Sci U S A 93(24):13864-9
33) Sette C, et al.  (2000) Mutational analysis suggests that activation of the yeast pheromone response mitogen-activated protein kinase pathway involves conformational changes in the Ste5 scaffold protein. Mol Biol Cell 11(11):4033-49
34) 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
35) Dard N and Peter M  (2006) Scaffold proteins in MAP kinase signaling: more than simple passive activating platforms. Bioessays 28(2):146-56
36) Bhattacharyya RP, et al.  (2006) The Ste5 scaffold allosterically modulates signaling output of the yeast mating pathway. Science 311(5762):822-6
37) Strickfaden SC, et al.  (2007) A mechanism for cell-cycle regulation of MAP kinase signaling in a yeast differentiation pathway. Cell 128(3):519-31