FIG. 6.

Specific SNARE complexes mediate fusion with the plasma membrane and prospore membrane. Secretory vesicle fusion with the plasma membrane is mediated by a heterotrimer consisting of Sso1p or Sso2p, Sec9p, and Snc1p or Snc2p (left panel). At the prospore membrane the fusion of secretory vesicles requires Sso1p, Spo20p (although Sec9p can substitute to a limited extent), and probably Snc1p or Snc2p. The roles of Snc1p and Snc2p in this process are inferred from the protein localization but have not been directly demonstrated (107).