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Related Concept Videos

SNAREs and Membrane Fusion01:43

SNAREs and Membrane Fusion

Once a transport vesicle has recognized its target organelle, the vesicular membrane needs to fuse with the target membrane to unload the cargo. Transmembrane proteins called SNAREs present on organelle membranes and their vesicles, mediate vesicle fusion.
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...
Fusion of Secretory Vesicles with the Plasma Membrane01:26

Fusion of Secretory Vesicles with the Plasma Membrane

Proteins and neurotransmitters in secretory vesicles can be released from a cell upon vesicle docking, priming, and fusion with the plasma membrane. Vesicles are docked and primed in preparation for the quick exocytosis of their contents in response to a stimulus. The fusion process is mainly carried out by a SNAP Receptor or SNARE complex, consisting of synaptobrevin, syntaxin-1, and SNAP-25.
In 1993, Jim Rothman proposed that the antiparallel pairing of vesicular and transmembrane SNAREs, or...
Protein Translocation Machinery on the ER Membrane01:28

Protein Translocation Machinery on the ER Membrane

The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Chemical Synapses01:26

Chemical Synapses

Chemical synapses are specialized sites between two neurons or between a neuron and a non-neuronal cell like a muscle, glandular or sensory cell.
Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is...
Chemical Synapses01:26

Chemical Synapses

Chemical synapses are specialized sites between two neurons or between a neuron and a non-neuronal cell like a muscle, glandular or sensory cell.
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Cotranslational Protein Translocation01:20

Cotranslational Protein Translocation

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Related Experiment Video

Updated: May 9, 2026

Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy
08:55

Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy

Published on: December 29, 2017

Subtle Interplay between synaptotagmin and complexin binding to the SNARE complex.

Junjie Xu1, Kyle D Brewer, Raquel Perez-Castillejos

  • 1Department of Biophysics, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA.

Journal of Molecular Biology
|July 13, 2013
PubMed
Summary
This summary is machine-generated.

Synaptotagmin-1 and complexin-I bind simultaneously to SNARE complexes, but full-length complexin-I is not displaced by synaptotagmin-1. This suggests a model where synaptotagmin-1 rearranges complexin-I

Keywords:
Ca(2+) triggeringHMQCHSQCITCMALSTCEPTIRFTROSYheteronuclear multiple quantum coherenceheteronuclear single quantum coherenceisothermal titration calorimetrymultiangle light scatteringneurotransmitter releaseprotein–membrane interactionsprotein–protein interactionssynaptic vesicle fusiontotal internal reflection fluorescencetransverse relaxation optimized spectroscopytris(2-carboxyethyl)phosphine

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In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal
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SNARE-mediated Fusion of Single Proteoliposomes with Tethered Supported Bilayers in a Microfluidic Flow Cell Monitored by Polarized TIRF Microscopy
10:58

SNARE-mediated Fusion of Single Proteoliposomes with Tethered Supported Bilayers in a Microfluidic Flow Cell Monitored by Polarized TIRF Microscopy

Published on: August 24, 2016

Related Experiment Videos

Last Updated: May 9, 2026

Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy
08:55

Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy

Published on: December 29, 2017

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal
06:45

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal

Published on: January 14, 2018

SNARE-mediated Fusion of Single Proteoliposomes with Tethered Supported Bilayers in a Microfluidic Flow Cell Monitored by Polarized TIRF Microscopy
10:58

SNARE-mediated Fusion of Single Proteoliposomes with Tethered Supported Bilayers in a Microfluidic Flow Cell Monitored by Polarized TIRF Microscopy

Published on: August 24, 2016

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Biophysics

Background:

  • Ca²⁺-triggered neurotransmitter release relies on SNARE complexes, synaptotagmin-1, and complexins.
  • Complexins regulate neurotransmitter release through inhibitory and active roles.
  • Previous models proposed synaptotagmin-1 displaces complexins to trigger exocytosis.

Purpose of the Study:

  • To investigate the interaction between synaptotagmin-1 C2 domains (C2AB) and complexin-I with SNARE complexes.
  • To clarify the mechanism of complexin-I displacement and its role in neurotransmitter release.
  • To propose a revised model for synaptotagmin-1 and complexin-I cooperation in exocytosis.

Main Methods:

  • Utilized diverse biophysical techniques to study protein-SNARE interactions.
  • Employed total internal reflection fluorescence microscopy (TIR-FM) to observe binding and displacement dynamics.
  • Analyzed binding affinities of full-length complexin-I and fragments to membrane-anchored SNARE complexes.

Main Results:

  • C2AB and complexin-I bind simultaneously to SNARE complexes but do not directly interact.
  • C2AB can displace a complexin-I fragment (Cpx26-83) from membrane-anchored SNAREs.
  • Full-length complexin-I binds more strongly and is not displaced by C2AB, indicating enhanced affinity via N/C-terminal interactions.

Conclusions:

  • The SNARE complex possesses distinct binding sites for both synaptotagmin-1 and complexin-I.
  • Full-length complexin-I's enhanced affinity prevents displacement by synaptotagmin-1.
  • A revised model suggests synaptotagmin-1 binding rearranges complexin-I's inhibitory helix without dissociation, enabling cooperative release.