The SNARE Complex from Yeast Is Partially Unstructured on the Membrane

jerry submitted, created time 4 months 3 days (www.structure.org)

Molecular recognition between cognate SNAREs leads to the formation of a four-helix bundle, which facilitates vesicle docking and membrane fusion. For a SNARE system involved in trafficking in yeast, target membrane (t-) SNARE Sso1p and vesicle associated (v-) SNARE Snc2p contribute one SNARE motif each, whereas another t-SNARE (Sec9) donates two N-terminal and C-terminal SNARE motifs (SN1 and SN2) to the helical bundle. By use of EPR, it is found that SN2 has a tendency to be uncoiled, leaving a significant population of the SNARE complexes to be partially unstructured on the membrane

2 comments | Blog It | Email It | Keywords: Sso1p Snc2p Sec9 membranes vesicle docking SNARE membrane fusion SN2 SNARE protein

Excess vacuolar SNAREs drive lysis and Rab bypass fusion

jiangyun submitted, created time 1 year 2 months (www.pnas.org)

Although concentrated soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) drive liposome fusion and lysis, the fusion of intracellular membranes also requires Rab GTPases, Rab effectors, SM proteins, and specific regulatory lipids and is accompanied by little or no lysis. To rationalize these findings, we generated yeast strains that overexpress all four vacuolar SNAREs (4SNARE++)

Submit comment | Blog It | Email It | Keywords: homotypic fusion and vacuole protein sor membrane fusion Rab GTPase yeast vacuoles

How Synaptotagmin Promotes Membrane Fusion

sciencebaby submitted, created time 1 year 5 months (www.sciencemag.org)

Synaptic vesicles loaded with neurotransmitters are exocytosed in a soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE)–dependent manner after presynaptic depolarization induces calcium ion (Ca2+) influx. The Ca2+ sensor required for fast fusion is synaptotagmin-1. The activation energy of bilayer-bilayer fusion is very high ({approx}40 kBT). We found that, in response to Ca2+ binding, synaptotagmin-1 could promote SNARE-mediated fusion by lowering this activation barrier by inducing high positive curvature in target membranes on C2-domain membrane insertion

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Persistent voids: a new structural metric for membrane fusion

claudia submitted, created time 1 year 6 months (bioinformatics.oxfordjournals.org)

Membrane fusion constitutes a key stage in cellular processes such as synaptic neurotransmission and infection by enveloped viruses. Current experimental assays for fusion have thus far been unable to resolve early fusion events in structural detail. We have previously used molecular dynamics simulations to develop mechanistic models of fusion by small lipid vesicles. Here, we introduce a novel structural measurement of vesicle topology and fusion geometry: persistent voids.

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Biologists prove critical step in membrane fusion

deirdre submitted, created time 1 year 7 months (www.physorg.com)

Membrane fusion, is fundamental to health and disease. It occurs at fertilization and is particularly critical to keep hormones circulating and brain cells firing. Membrane fusion is also how HIV and other viruses infect cells. Scientists discovered that the membranes of the egg and the vesicles are hemifused – a state where the membranes are shared but the contents remain separate. Using fluorescent dyes and a high-resolution microscope, the researchers show that hemifusion is surprisingly stable in live cells.

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