A decomposition of the Saccharomyces cerevisiae pheromone-response (mating) MAP kinase cascade, the fungal realization of the generic three-tier MAP kinase relay (MODULE:mapk_relay). Mating pheromone (a-factor or alpha-factor) activates a G-protein-coupled receptor (Ste2/Ste3); the released G-protein beta-gamma dimer and the PAK kinase Ste20, organized on the scaffold Ste5, activate the MAP3K Ste11, which phosphorylates the MAP2K Ste7, which dually phosphorylates the MAPK Fus3 (and the partially redundant Kss1) on its TEY activation-loop motif. Active Fus3 phosphorylates the transcription factor Ste12 and the cell-cycle inhibitor Far1, driving the mating transcriptional program, G1 arrest, and polarized shmoo formation for conjugation. The kinase relay - Ste11 -> Ste7 -> Fus3 - is declared as an inner bundle that `conforms_to` mapk_relay, while the pheromone/GPCR input and the Ste12/Far1 output are this cascade's free extensions around the conforming core. Grounded in GO:0000750 (pheromone-dependent signal transduction involved in conjugation with cellular fusion).
This module is the Saccharomyces cerevisiae mating-pathway realization of the generic three-tier MAP kinase relay (MODULE:mapk_relay): the inner `fus3_relay` node bundles the Ste11 -> Ste7 -> Fus3 tiers and declares conformance to that motif, while the pheromone/GPCR input and the downstream Ste12/Far1 output are this cascade's free extensions around the conforming core. The cascade is organized on the Ste5 scaffold. Representative UniProt members (Ste11 P23561, Ste7 P06784, Fus3 P16892, Kss1 P14681) were verified against UniProt. No matching UniProt-seed PAINT IBD rows were found in the local interpro/panther cache for these S. cerevisiae exemplars, so this species-specific cascade is not assigned a PTN ancestry anchor in this pass.
All recommended fields populated.
✗ none found
No MODULE:scer_mating_fus3_cascade deep-research report alongside the module YAML.
2 leaf node(s) with no concrete protein grounding:
✓ every declared conforms_to bundle matches its template motif.
0 complete review(s) · 0 with deep research · 4 missing review · 0 reviewed but lacking deep research
| Gene | Review | Complete | Deep research |
|---|---|---|---|
| Ste7 P06784 | ✗ | — | — |
| Kss1 P14681 | ✗ | — | — |
| Fus3 P16892 | ✗ | — | — |
| Ste11 P23561 | ✗ | — | — |
Mating pheromone activates the GPCR Ste2/Ste3; the freed G-protein beta-gamma dimer recruits Ste20 (PAK) and the Ste5 scaffold to activate the MAP3K Ste11.
Couples pheromone/GPCR signaling to the Fus3 relay.
The three-tier kinase relay of the mating cascade: Ste11 (MAP3K) phosphorylates Ste7 (MAP2K), which dually phosphorylates Fus3 (MAPK, with partially redundant Kss1) on its TEY activation-loop motif. The relay is assembled on the Ste5 scaffold.
Ste11 phosphorylates and activates Ste7.
Top kinase tier; activates Ste7.
The dual-specificity MAP2K Ste7 phosphorylates Fus3 on both threonine and tyrosine of its TEY motif.
Middle kinase tier; dual-specificity activation of Fus3.
Dually phosphorylated Fus3 (with partially redundant Kss1) becomes an active proline-directed serine/threonine kinase acting on mating substrates.
Effector kinase transducing the pheromone signal to substrates.
Active Fus3 phosphorylates the transcription factor Ste12 (de-repressing it by inactivating Dig1/Dig2) and the cell-cycle inhibitor Far1, driving the mating transcriptional program, G1 arrest, and polarized shmoo formation.
Converts Fus3 activity into the Ste12-driven mating gene program.