Ste20

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Contents 1 About Ste20 2 Reactions 3 Species Representation 3.1 Molecule Type 3.2 Model Seed

About Ste20

• Ste20 binds Ste4 with residues 878-880. Leeuw et al. 1998 PMID 9428767

• Ste20 is part of the p21-activated kinase (PAK) family of kinases. Lamson et al. 2002 PMID 11940652

• Ste20 CRIB domain at residues 334-369 interacts the kinase domain of Ste20, inhibiting the kinase domain's activity. It's not known if the CRIB/kinase domain interactions occur inter- or intra-molecularly. Lamson et al. 2002 PMID 11940652

• Ste20 CRIB domain interacts with GTP-bound Cdc42. The interaction with Cdc42 relieves the autoinhibition of the kinase domain. Lamson et al. 2002 PMID 11940652

• The activity of immunoprecipitated Ste20 is largely unaffected by prior treatment of the cells with pheromone. Wu et al. 1995 PMID 7608157; Lamson et al. 2002 PMID 11940652

• A single mutation (D772T) in Cla4 (another member of the PAK family) can restore mating in a ste20Δ strain. Keniry and Sprague. 2003 PMID 12588977

• Ste20 is phosphorylated by Cln2-Cdc28 during the S phase of the cell cycle. This phosphorylation does not appear to affect in vitro Ste20 kinase activity using immunoprecipitated Ste20. Wu et al. 1998 PMID 9774429

• GFP-Ste20 is mainly found at the bud site in late G₁, and throughout bud growth. Wu et al. 1998 PMID 9774429

• Thirteen phosphorylation site on Ste20 have been at least partially identified: Ser418, (Ser422 or Thr423), Ser502, three sites in a tryptic peptide spanning residues 506–530, Ser547, (Ser551, Thr552, or Thr555), Ser562, Thr573, Ser585, Thr773, and (Ser861 or Thr863). Oda et al. 1999 PMID 10359756
  • These sites are differentially phosphorylated in CLN2⁺ and cln2^- cells

• Mutations within the CRIB domain that selectively eliminate the interaction between Ste20 and Cdc42 greatly decrease mating pathway activity. Lamson et al. 2002 PMID 11940652; Ash et al. 2003 PMID 12586692
  • This implies that Cdc42 plays an important role in Ste20 activation.

• Deletion of the CRIB domain of Ste20 eliminates Cdc42-binding and has little effect on mating signal transduction (although greatly reduces response to nitrogen starvation and cell-cell adhesion during mating), making the role of Cdc42 somewhat unclear. Peter et al. 1996 PMID 9003780; Leberer et al. 1997 PMID 9009270; Lamson et al. 2002 PMID 11940652

• Ste20 is phosphorylated by Cln2-Cdc28. Wu et al. 1998 PMID 9774429
  • Ste20 is phosphorylated by Cln2-Cdc28 in vitro.
  • Overexpression of Cln2 results in hyperphosphorylation of Ste20.

• Although the cellular localization of Ste20 is regulated in a cell-cycle dependent manner, the activity of immunoprecipitated Ste20 is independent of cell-cycle. Wu et al. 1998 PMID 9774429

• The interaction between Bem1 and Ste20 is also important for proper Ste20 localization, and has a moderate effect of mating signaling. Winters and Pryciak 2005 PMID 15743816

Reactions

Ste4:Ste18/Ste20 interaction
MAPK phosphorylation cascade
Protein dilution/synthesis due to cell growth

Species Representation

Molecule Type

Ste20(Ste4_site, Ste11_site)

Model Seed

Ste20(Ste4_site, Ste11_site) Ste20_tot_conc