Synaptotagmin-1 is known to accelerate membrane fusion during neuronal exocytosis in response to Ca2+, but how it does this is unclear. By probing the activity of synaptotagmin-1 under conditions of low ionic strength, it is now shown that SNARE-mediated fusion is dependent on synaptotagmin-1, which tethers liposomes together but at distances too far for fusion. Ca2+ then induces synaptotagmin-1 to bring the liposomes closer together, allowing fusion to proceed.
- Geert van den Bogaart
- Shashi Thutupalli
- Reinhard Jahn
