Complexin cross-links prefusion SNAREs into a zigzag array

Structural studies of complexin bound to a mimetic of a prefusion SNARE complex provide insight into how complexin 'clamps' SNARE complex assembly, thereby inhibiting membrane fusion. While the central helix of complexin is anchored to a SNARE complex, its accessory helix extends away and bridges to a second SNARE complex, generating a zigzag array incompatible with fusion.