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- EMDB-76034: Low resolution cryo-EM structure of Munc18 bound to Syntaxin and ... -

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Basic information

Entry
Database: EMDB / ID: EMD-76034
TitleLow resolution cryo-EM structure of Munc18 bound to Syntaxin and SNAP25 in nanodiscs
Map data
Sample
  • Complex: Munc18 bound to syntaxin and SNAP25 in nanodiscs
KeywordsSNARE / membranes / fusion / Syntaxin / Munc18 / EXOCYTOSIS
Biological speciesRattus norvegicus (Norway rat)
Methodsingle particle reconstruction / cryo EM / Resolution: 12.7 Å
AuthorsKreutzberger MA / Tomaka W / Bao H / Kiessling V / Tamm LK
Funding support United States, 1 items
OrganizationGrant numberCountry
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)P01 GM072694. United States
CitationJournal: bioRxiv / Year: 2026
Title: Munc18 binds to and organizes membrane-bound acceptor Q-SNARE complexes in a fashion that depends on the membrane's lipid composition.
Authors: Weronika Tomaka / Mark Kreutzberger / Huan Bao / Volker Kiessling / Lukas K Tamm /
Abstract: Neuroendocrine cells communicate with other cells by releasing neurotransmitters or hormones by exocytosis, which involves SNARE-mediated fusion between secretory vesicles and the plasma membranes of ...Neuroendocrine cells communicate with other cells by releasing neurotransmitters or hormones by exocytosis, which involves SNARE-mediated fusion between secretory vesicles and the plasma membranes of the secreting cells. In neurons two plasma membrane SNARE proteins, Syntaxin-1a and SNAP25, join with the vesicle membrane SNARE protein Synaptobrevin-2 to form a four-helix bundle, which drives membrane fusion. The assembly of these SNAREs, which is highly orchestrated in cells, has been intensely studied in solution using fragments of the SNARE proteins without their transmembrane domains or lipid anchors. However, in cell and model membranes, Syntaxin and SNAP25 are known to oligomerize and cluster, and little is known about how clustering affects their incorporation into SNARE complexes. In cells, the SM protein Munc18 has been implicated in aiding secretory vesicle docking and facilitating SNARE complex assembly through its interactions with Syntaxin. To understand how Munc18 orchestrates SNARE complex assembly on membranes, we employed protein reconstitution in model membranes as well as biochemical and biophysical assays to show that lipid-dependent oligomerization of Syntaxin affects Munc18-Syntaxin binding and SNAP25 insertion into the plasma membrane acceptor SNARE complex. We showcase the consequences of the different modes of Munc18-Syntaxin and SNAP25 interaction on Syntaxin's oligomerization and orientation relative to the membrane surface, as well as on docking and fusion of purified insulin granules. We also determined low-resolution structures by cryoEM in nanodiscs and on the surface of proteoliposomes of membrane-bound assembly states of Munc18/Syntaxin and Munc18/Syntaxin/SNAP25 complexes.
History
DepositionMar 12, 2026-
Header (metadata) releaseAug 12, 2026-
Map releaseAug 12, 2026-
UpdateAug 12, 2026-
Current statusAug 12, 2026Processing site: RCSB / Status: Released

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Structure visualization

Supplemental images

emd_76034.png

Downloads & links

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Map

FileDownload / File: emd_76034.map.gz / Format: CCP4 / Size: 64 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
Projections & slices

Image control

Size
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AxesZ (Sec.)Y (Row.)X (Col.)
1.07 Å/pix.
x 256 pix.
= 272.64 Å		1.07 Å/pix.
x 256 pix.
= 272.64 Å		1.07 Å/pix.
x 256 pix.
= 272.64 Å

Surface

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Images are generated by Spider.

Voxel sizeX=Y=Z: 1.065 Å
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Histogram

Histogram (log scale)
Contour LevelBy AUTHOR: 0.0266
Minimum - Maximum-0.05028397 - 0.16449761
Average (Standard dev.)0.004393575 (±0.017798098)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions256256256
Spacing256256256
CellA=B=C: 272.64 Å
α=β=γ: 90.0 °

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Supplemental data

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Half map: #2

Fileemd_76034_half_map_1.map
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Half map: #1

Fileemd_76034_half_map_2.map
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Sample components

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Entire : Munc18 bound to syntaxin and SNAP25 in nanodiscs

EntireName: Munc18 bound to syntaxin and SNAP25 in nanodiscs
Components
  • Complex: Munc18 bound to syntaxin and SNAP25 in nanodiscs

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Supramolecule #1: Munc18 bound to syntaxin and SNAP25 in nanodiscs

SupramoleculeName: Munc18 bound to syntaxin and SNAP25 in nanodiscs / type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1
Source (natural)Organism: Rattus norvegicus (Norway rat)

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Experimental details

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Structure determination

Methodcryo EM
Processingsingle particle reconstruction
Aggregation stateparticle

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Sample preparation

BufferpH: 7.4
VitrificationCryogen name: ETHANE

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Electron microscopy

MicroscopeTFS KRIOS
Image recordingFilm or detector model: GATAN K3 (6k x 4k) / Average electron dose: 60.0 e/Å2
Electron beamAcceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron opticsIllumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Nominal defocus max: 2.5 µm / Nominal defocus min: 1.0 µm
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company

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Image processing

CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Startup modelType of model: NONE / Details: ab initio
Final reconstructionResolution.type: BY AUTHOR / Resolution: 12.7 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC / Number images used: 11988
Initial angle assignmentType: MAXIMUM LIKELIHOOD
Final angle assignmentType: MAXIMUM LIKELIHOOD
FSC plot (resolution estimation)

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