Figure 8.

Model for Bsd2-dependent ubiquitination by Rsp5. (A) Self-modification of Bsd2 requires the formation of a complex with Rsp5 mediated by the PY1-WW2 and PY2-WW3 interactions (indicated by gray bars). The subsequent association of either Cps1 (Bi) or Tre1 (Bii) allows their ubiquitination, although this is still mediated by PY1-WW2 and PY2-WW3. (C) Modification of Smf1 requires first the association of Rsp5/Bsd2 with Tre1 and a subsequent rearrangement that allows the PY motif of Tre1 to interact with WW3 displacing PY2 in Bsd2. Cps1 and Tre1 are depicted highly schematically, with the luminal domains omitted.