Helical extension of the neuronal SNARE complex into the membrane

Stein, Alexander; Weber, Gert; Wahl, Markus C.; Jahn, Reinhard

doi:10.1038/nature08156

Cited by 393 publications

(509 citation statements)

References 49 publications

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“…In case of the formation of a single SNARE complex out of syntaxin, SNAP-25, and synaptobrevin, the 'minimal machinery' required for membrane fusion (70), a free energy release of ΔG ¼ 18 k B T has been measured by isothermal titration calorimetry (65) and ΔG ¼ 35 k B T by surface force apparatus (64), respectively. Based on molecular size, the maximum interaction distance at which the SNARE complex could nucleate is in the range of 5-20 nm (71,72), which has to be compared to the 0.9 nm of critical distance for hemifusion in our lipid compositions. The short-range repulsive forces that need to be overcome to bring membranes to close proximity prior to fusion are quantified by the hydration force parameters.…”

Section: Discussionmentioning

confidence: 99%

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Aeffner

Reusch²,

Weinhausen³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

164

246

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We have used X-ray diffraction on the rhombohedral phospholipid phase to reconstruct stalk structures in different pure lipids and lipid mixtures with unprecedented resolution, enabling a quantitative analysis of geometry, as well as curvature and hydration energies. Electron density isosurfaces are used to study shape and curvature properties of the bent lipid monolayers. We observe that the stalk structure is highly universal in different lipid systems. The associated curvatures change in a subtle, but systematic fashion upon changes in lipid composition. In addition, we have studied the hydration interaction prior to the transition from the lamellar to the stalk phase. The results indicate that facilitating dehydration is the key to promote stalk formation, which becomes favorable at an approximately constant interbilayer separation of 9.0 AE 0.5 Å for the investigated lipid compositions.curvature energy | hydration force | lipid bilayer | E xocytosis, intracellular transport, neurotransmission, fertilization, or viral entry, require that two membranes merge into one. This event, membrane fusion, involves a complex interplay of different membrane lipids, proteins, and water molecules on length scales of few nm. Following the "lipidic pore hypothesis", it is now well accepted that membrane fusion involves a sequence of lipidic nonbilayer intermediates, whose formation is catalyzed and guided by a specialized protein machinery (1, 2). A stage termed "hemifusion" in which the lipids of the outer leaflets of two membrane-enclosed compartments about to fuse can mix, whereas the inner leaflets and the enclosed content remain unaltered (3), has been confirmed by a variety of methods including conical electron tomography (4) and, more indirectly; e.g., by electron spin resonance (5) and fluorescence recovery after photobleaching (6). Studying the fusion of protein-free bilayers of well defined lipid composition can contribute useful insights into the physical principles governing the merger of their more complex biological counterparts and clarify the effect of individual lipid species.The first connection between two lipid bilayers is the so-called stalk sketched in Fig. 1A (7). The proximal lipid monolayers have merged into one strongly curved monolayer, whereas the distal ones are still separated and intact. A persistent problem in membrane biophysics is to determine the precise structure of stalks and the free energy barrier for stalk formation. In a long series of papers (8-16), this determination has been attempted within the framework of the continuum theory of membrane elasticity (17, 18). More recently, with the advent of sufficient computational power, simulations including molecular details have become feasible [e.g. (19, 20) and references therein]. While stalk formation between lipid bilayers in close contact is generally accepted as the initial step in possibly all membrane fusion reactions (7), the subsequent stages from stalk to complete fusion are still debated and different pathways may exist (21)....

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Section: Discussionmentioning

confidence: 99%

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Aeffner

Reusch²,

Weinhausen³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

164

246

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“…During membrane fusion, SNARE proteins on opposing membranes coil together to form a highly stable four-helix bundle complex with conserved leucine-zipper-like layers embedding an ionic zero-layer at the center [1][2][3][4][5][6]. The SNARE complex is believed to be the minimum machinery necessary to drive membrane fusion [7].…”

Section: Introductionmentioning

confidence: 99%

Cryo-EM structure of SNAP-SNARE assembly in 20S particle

et al. 2015

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N-ethylmaleimide-sensitive factor (NSF) and α soluble NSF attachment proteins (α-SNAPs) work together within a 20S particle to disassemble and recycle the SNAP receptor (SNARE) complex after intracellular membrane fusion. To understand the disassembly mechanism of the SNARE complex by NSF and α-SNAP, we performed single-particle cryo-electron microscopy analysis of 20S particles and determined the structure of the α-SNAP-SNARE assembly portion at a resolution of 7.35 Å. The structure illustrates that four α-SNAPs wrap around the single left-handed SNARE helical bundle as a right-handed cylindrical assembly within a 20S particle. A conserved hydrophobic patch connecting helices 9 and 10 of each α-SNAP forms a chock protruding into the groove of the SNARE four-helix bundle. Biochemical studies proved that this structural element was critical for SNARE complex disassembly. Our study suggests how four α-SNAPs may coordinate with the NSF to tear the SNARE complex into individual proteins.

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“…If indeed FPs adopt a TM orientation, then one might envision a mechanism akin to SNARE proteins (50)(51)(52)(53), in which both the target and vesicular proteins have TM helices that associate as membrane fusion progresses. Accordingly, we investigate herein a class I fusogenic protein, F, from parainfluenza virus 5 (PIV5), which, like influenza virus HA and HIV gp41, has an N-terminal FP in the mature, cleaved protein (3).…”

mentioning

confidence: 99%

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

Donald¹,

Zhang

Fiorin

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Membrane fusion is required for diverse biological functions ranging from viral infection to neurotransmitter release. Fusogenic proteins increase the intrinsically slow rate of fusion by coupling energetically downhill conformational changes of the protein to kinetically unfavorable fusion of the membrane-phospholipid bilayers. Class I viral fusogenic proteins have an N-terminal hydrophobic fusion peptide (FP) domain, important for interaction with the target membrane, plus a C-terminal transmembrane (C-term-TM) helical membrane anchor. The role of the water-soluble regions of fusogenic proteins has been extensively studied, but the contributions of the membrane-interacting FP and C-term-TM peptides are less well characterized. Typically, FPs are thought to bind to membranes at an angle that allows helix penetration but not traversal of the lipid bilayer. Here, we show that the FP from the paramyxovirus parainfluenza virus 5 fusogenic protein, F, forms an N-terminal TM helix, which self-associates into a hexameric bundle. This FP also interacts strongly with the C-term-TM helix. Thus, the fusogenic F protein resembles SNARE proteins involved in vesicle fusion by having water-soluble coiled coils that zipper during fusion and TM helices in both membranes. By analogy to mechanosensitive channels, the force associated with zippering of the water-soluble coiled-coil domain is expected to lead to tilting of the FP helices, promoting interaction with the C-term-TM helices. The energetically unfavorable dehydration of lipid headgroups of opposing bilayers is compensated by thermodynamically favorable interactions between the FP and C-term-TM helices as the coiled coils zipper into the membrane phase, leading to a pore lined by both lipid and protein.T he basic mechanisms of viral membrane fusion have been studied extensively, but major gaps remain in our understanding of the relative roles of lipidic intermediates and viral fusogenic proteins in lowering the energy barrier for the overall process (1-4). The most common mechanistic hypothesis concerning enveloped viral fusion is that fusogenic proteins primarily serve to bring the target cell and viral membranes into proximity. Fusion occurs in a multistep process, in which the virus first binds to a specific receptor; this event and/or other environmental cues then cause a conformational change in the protein, leading to a metastable state with an exposed hydrophobic fusion peptide (FP) that binds to the target membrane. Once engaged with the bilayer, a second energetically favorable conformational change in the fusogenic protein then exerts a force pulling the FP toward the viral membrane, in effect reeling the host and viral membranes together.The conformational changes involved in the water-soluble portions of viral fusogenic proteins have been largely elucidated, but the roles of the membrane-binding FP and the C-terminal transmembrane (C-term-TM) anchor are less clear. After the crystal structure of the prefusogenic form of influenza hemagglutinin (HA) was solved...

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Helical extension of the neuronal SNARE complex into the membrane

Cited by 393 publications

References 49 publications

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Cryo-EM structure of SNAP-SNARE assembly in 20S particle

Transmembrane orientation and possible role of the fusogenic peptide from parainfluenza virus 5 (PIV5) in promoting fusion

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