Imported:YPM/Fus3/Gpa1/Ste4 interactions

Fus3/Gpa1/Ste4 interactions

Active Fus3 appears to bind active Gpa1. Metodiev et al. 2002 PMID 12029138
- His-tagged Gpa1 expressed and purified from E. coli is able to pull Fus3-Myc out of cell lysates of pheromone treated cells.
  - More Fus3-Myc is recovered when Gpa1 is pre-treated with GTP-γ-S.
- His-tagged Gpa1 expressed and purified from E. coli fails to pull Fus3-Myc out of cell lysates of cells that were not exposed to pheromone.
- Gpa1 contains a putative MAPK-binding sequence at residues 21-33.
Mutation of the putative MAPK-binding sequence in Gpa1 (K21E R22E) reduces the mating efficiency to 1/15^th of WT efficiency. Metodiev et al. 2002 PMID 12029138
- This mutation also decreases Fus3 dependent phosphorylation of Ste4.
Gpa1(K21E R22E) results in wild-type Fus3-GFP localization in the absence of pheromone, and higher than normal nuclear localization upon pheromone treatment. Blackwell et al. 2003 PMID 12556475

Since the purpose and mechanism of this interaction is not understood, we will omit it from the model.