Coarse-grain simulations reveal movement of the synaptobrevin C-terminus in response to piconewton forces

Manfred Lindau, Benjamin A. Hall, Alan Chetwynd, Oliver Beckstein, Mark S P Sansom

Research output: Contribution to journalArticle

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Abstract

Fusion of neurosecretory vesicles with the plasma membrane is mediated by SNARE proteins, which transfer a force to the membranes. However, the mechanism by which this force transfer induces fusion pore formation is still unknown. The neuronal vesicular SNARE protein synaptobrevin 2 (syb2) is anchored in the vesicle membrane by a single C-terminal transmembrane (TM) helix. In coarse-grain molecular-dynamics simulations, self-assembly of the membrane occurred with the syb2 TM domain inserted, as expected from experimental data. The free-energy profile for the position of the syb2 membrane anchor in the membrane was determined using umbrella sampling. To predict the free-energy landscapes for a reaction pathway pulling syb2 toward the extravesicular side of the membrane, which is the direction of the force transfer from the SNARE complex, harmonic potentials were applied to the peptide in its unbiased position, pulling it toward new biased equilibrium positions. Application of piconewton forces to the extravesicular end of the TM helix in the simulation detached the synaptobrevin C-terminus from the vesicle's inner-leaflet lipid headgroups and pulled it deeper into the membrane. This C-terminal movement was facilitated and hindered by specific mutations in parallel with experimentally observed facilitation and inhibition of fusion. Direct application of such forces to the intravesicular end of the TM domain resulted in tilting motion of the TM domain through the membrane with an activation energy of ∼70 kJ/mol. The results suggest a mechanism whereby fusion pore formation is induced by movement of the charged syb2 C-terminus within the membrane in response to pulling and tilting forces generated by C-terminal zippering of the SNARE complex.

Original languageEnglish (US)
Pages (from-to)959-969
Number of pages11
JournalBiophysical Journal
Volume103
Issue number5
DOIs
StatePublished - Sep 5 2012

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R-SNARE Proteins
Vesicle-Associated Membrane Protein 2
Membranes
SNARE Proteins
Molecular Dynamics Simulation
Cell Membrane

ASJC Scopus subject areas

  • Biophysics

Cite this

Coarse-grain simulations reveal movement of the synaptobrevin C-terminus in response to piconewton forces. / Lindau, Manfred; Hall, Benjamin A.; Chetwynd, Alan; Beckstein, Oliver; Sansom, Mark S P.

In: Biophysical Journal, Vol. 103, No. 5, 05.09.2012, p. 959-969.

Research output: Contribution to journalArticle

Lindau, Manfred ; Hall, Benjamin A. ; Chetwynd, Alan ; Beckstein, Oliver ; Sansom, Mark S P. / Coarse-grain simulations reveal movement of the synaptobrevin C-terminus in response to piconewton forces. In: Biophysical Journal. 2012 ; Vol. 103, No. 5. pp. 959-969.
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