Synaptotagmin oligomers are necessary and can be sufficient to form a Ca2+ -sensitive fusion clamp.
The buttressed-ring hypothesis, supported by recent cryo-electron tomography analysis of docked synaptic-like vesicles in neuroendocrine cells, postulates that prefusion SNAREpins are stabilized and organized by Synaptotagmin (Syt) ring-like oligomers. Here, we use a reconstituted single-vesicle fusion analysis to test the prediction that destabilizing the Syt1 oligomers destabilizes the clamp and results in spontaneous fusion in the absence of Ca2+ . Vesicles in which Syt oligomerization is compromised by a ring-destabilizing mutation dock and diffuse freely on the bilayer until they fuse spontaneously, similar to vesicles containing only v-SNAREs. In contrast, vesicles containing wild-type Syt are immobile as soon as they attach to the bilayer and remain frozen in place, up to at least 1 h until fusion is triggered by Ca2+ .
['Ramakrishnan|Sathish|S|', 'Bera|Manindra|M|', 'Coleman|Jeff|J|', 'Krishnakumar|Shyam S|SS|', 'Pincet|Frederic|F|', 'Rothman|James E|JE|']
D000818:Animals D002118:Calcium D020285:Cryoelectron Microscopy D055032:Electron Microscope Tomography D008561:Membrane Fusion D009154:Mutation D055503:Protein Multimerization D050600:SNARE Proteins D013572:Synaptic Vesicles D050863:Synaptotagmin I
Synaptotagmin fusion clamp SNARE proteins calcium single-vesicle analysis