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About Kss1

  • Kss1 was genetically identified in the Thorner lab as a kinase required for efficient cell fusion and mating. Courchesne et al. 1989 PMID 2673544
  • Kss1 is a small protein kinase (368 residues) that has 56% amino acid sequence identity with Fus3. Ma et al. 1995 PMID 7579701
  • Kss1 was hypothesized to be the invasive specific MAPK as cells lacking Kss1 are incapable of penetrating a superficial agar surface (Roberts and Fink 1994 PMID 8001818), and unlike Fus3, Kss1 is expressed in both haploids and diploids (Bardwell et al. 1994 PMID 7813763).
  • Kss1 appears to be stable with a half life >2h, as its levels in cyclohiximide treated cells (in the presence or absence of pheromone) remained approximately constant according to unpublished results. Ma et al. 1995 PMID 7579701
  • Cycloheximide treatment results in the levels of phosphorylated Kss1 peaking about 5 minutes after pheromone exposure, whereas in the absence of cycloheximide peak levels of phosphorylated Kss1 occur >60 min after pheromone exposure. Ma et al. 1995 PMID 7579701
  • Kss1 is phosphorylated at Thr183 and Tyr185 in response to pheromone. Tyr185 appears to be more strongly phosphorylated than Thr183. Ma et al. 1995 PMID 7579701
  • Kss1 likely requires phosphorylation at both T183 and Y185 for kinase activity. This has been demonstrated for another MAPK (rat Erk2). Ferrell and Bhatt. 1997 PMID 9228083
  • Activated Kss1-Myc phosphorylates purified Ste12-Flag at five times the rate that it phosphorylates His-Far1. The proteins were expressed and purified from instect cells. Breitkreutz et al. 2001 PMID 11525741
  • Activated Kss1-Myc phosphorylates Ste12-Flag at half the rate that Fus3-Myc does, and phosphorylates Far1 at one tenth the rate that Fus3-Myc does. This conclusion requires that the purified Kss1-Myc and Fus3-Myc are both maximally (or at least equivalently) activated. Breitkreutz et al. 2001 PMID 11525741
  • Studies with ERK2 show that peptides containing the MAPK-docking site (from MEK1, MEK2, Ste7, Elk-1 and (MKP)-2) compete for binding to ERK2, suggesting that they all bind to the same region on ERK2. Bardwell et al. 2003 PMID 12529172
  • Kss1 (but none of the other MAPKs in yeast) is required for filamentation in diploids. Kss1 kinase activity is required for invasive growth in haploids. Madhani et al. 1997 PMID 9393860
  • Kss1 plays an inhibitory role in filamentation (in addition to its activating role), which acts on Ste12-Tec1. Madhani et al. 1997 PMID 9393860
    • Ste12 coprecipitates with HA-tagged Kss1, although WT Kss1 coprecipitated less Ste12 than kinase dead Kss1(K42R).
  • Invasive (haploids) and pseudohyphal (diploids) growth are both repressed by unactivated Kss1. Activation of Kss1 by Ste7 not only relieves this repression, but also activates both invasive and pseudohyphal growth. Cook et al. 1997 PMID 9363895


Sst2 synthesis/degradation
Ste5/MAPK cascade interactions
MAPK phosphorylation cascade
MAPK/phosphatase interactions
Ste11 synthesis/degradation
Ste7/MAPK interactions
Dig1/Dig2/Ste12/Tec1 interactions
Dig1/Dig2/Ste12 phosphorylation
Far1/MAPK interactions
Non-specific dephosphorylation
Protein dilution/synthesis due to cell growth

See also MAPK/target interaction properties

Species Representation

Molecule Type

Kss1(docking_site, T183~none~PO4, Y185~none~PO4)

Model Seed

Kss1(docking_site, T183~none, Y185~none) Kss1_tot_conc

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