Energetics and dynamics of SNAREpin folding across lipid bilayers.
Membrane fusion occurs when SNAREpins fold up between lipid bilayers. How much energy is generated during SNAREpin folding and how this energy is coupled to the fusion of apposing membranes is unknown. We have used a surface forces apparatus to determine the energetics and dynamics of SNAREpin formation and characterize the different intermediate structures sampled by cognate SNAREs in the course of their assembly. The interaction energy-versus-distance profiles of assembling SNAREpins reveal that SNARE motifs begin to interact when the membranes are 8 nm apart. Even after very close approach of the bilayers (approximately 2-4 nm), the SNAREpins remain partly unstructured in their membrane-proximal region. The energy stabilizing a single SNAREpin in this configuration (35 k(B)T) corresponds closely with the energy needed to fuse outer but not inner leaflets (hemifusion) of pure lipid bilayers (40-50 k(B)T).
Li
Feng
F
Laboratoire de Physique Statistique, Unité Mixte de Recherche 8550, Centre National de la Recherche Scientifique associée aux Universités Paris VI et Paris VII, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France.
Pincet
Frédéric
F
Perez
Eric
E
Eng
William S
WS
Melia
Thomas J
TJ
Rothman
James E
JE
Tareste
David
D
D000818:Animals; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D051379:Mice; D011487:Protein Conformation; D017510:Protein Folding; D051381:Rats; D050600:SNARE Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013499:Surface Properties
D008051:Lipid Bilayers; D050600:SNARE Proteins