FIG. 8.
Model of Pak1-dependent activation of Snf1 kinase. In the presence of a high glucose concentration, Snf1 kinase is in a complex with the Reg1 protein, which recruits protein phosphatase Glc7 (not shown). The Reg1/Glc7 complex dephosphorylates Snf1 threonine 210 (21). In the presence of a low glucose concentration, Pak1 associates with the Snf1 kinase complex and phosphorylates Snf1 on threonine 210. Snf4 also participates in activation of the Snf1 kinase through direct interaction with the Snf1 regulatory domain. Once activated, Snf1 kinase phosphorylates its beta subunit (Sip1, Sip2, or Gal83), the Reg1 protein, and additional substrates, such as Mig1 (not shown).