Skip to main content
. Author manuscript; available in PMC: 2013 Aug 7.
Published in final edited form as: Science. 2009 Jan 23;323(5913):474–477. doi: 10.1126/science.1161748

Figure 2.

Figure 2

(A) The zippering model for SNARE-catalyzed membrane fusion. Three helices anchored in one membrane (the t-SNARE) assemble with the fourth helix anchored in the other membrane (v-SNARE) to form trans-SNARE complexes, or SNAREpins. Assembly proceeds progressively from the membrane-distal N-termini towards the membrane-proximal C-termini of the SNAREs. This generates an inward force vector (F) that pulls the bilayers together, forcing them to fuse. Complete zippering is sterically prevented until fusion occurs, so that fusion and the completion of zippering are thermodynamically coupled. (B) Therefore, when fusion has occurred, the force vanishes and the SNAREs are in the low energy cis-SNARE complex.