Membrane fusion proceeds via the distinct stages of docking, hemifusion and fusion pore opening, which requires the coordinated actions of Rab, SNARE and SM proteins. Studies with yeast vacuoles now reveal that the SM protein Vps33 promotes fusion pore opening by enhancing the fusogenic activity of a SNARE complex, suggesting that SM proteins may be integral parts of the membrane fusion machinery.
- Michel Pieren
- Andrea Schmidt
- Andreas Mayer