A conformational switch in complexin is required for synaptotagmin to trigger synaptic fusion

Comparison of the prefusion and postfusion structures of complexin associated with SNAREs reveals a conformational switch in complexin, which is triggered by the zippering of three key Asp residues in the “switch” region of v-SNAREs into t-SNAREs. This causes complexin to move its accessory helix, thereby releasing the clamped state. This switch is triggered when the calcium sensor synaptotagmin binds calcium ions.