Journal of Biomolecular NMR

, Volume 41, Issue 1, pp 43–54 | Cite as

NMR analysis of the closed conformation of syntaxin-1

  • Xiaocheng Chen
  • Jun Lu
  • Irina Dulubova
  • Josep Rizo


The Sec1/Munc18 (SM) protein Munc18-1 and the SNAREs syntaxin-1, SNAP-25 and synaptobrevin form the core of the membrane fusion machinery that triggers neurotransmitter release. Munc18-1 binds to syntaxin-1 folded into a closed conformation and to the SNARE complex formed by the three SNAREs, which involves an open syntaxin-1 conformation. The former interaction is likely specialized for neurotransmitter release, whereas SM protein/SNARE complex interactions are likely key for all types of intracellular membrane fusion. It is currently unclear whether the closed conformation is highly or only marginally populated in isolated syntaxin-1, and whether Munc18-1 stabilizes the close conformation or helps to open it to facilitate SNARE complex formation. A detailed NMR analysis now suggests that the closed conformation is almost quantitatively populated in isolated syntaxin-1 in the absence of oligomerization, and indicates that its structure is very similar to that observed previously in the crystal structure of the Munc18-1/syntaxin-1 complex. Moreover, we demonstrate that Munc18-1 binding prevents opening of the syntaxin-1 closed conformation. These results support a model whereby the closed conformation constitutes a key intrinsic property of isolated syntaxin-1 and Munc18-1 binding stabilizes this conformation; in this model, Munc18-1 plays in addition an active role in downstream events after another factor(s) helps to open the syntaxin-1 conformation.


Conformational exchange Membrane traffic Munc18 Neurotransmitter release Syntaxin TROSY 



Correlation spectroscopy


Fluorescence resonance energy transfer


Heteronuclear single quantum coherence


Nuclear Overhauser effect spectroscopy


N-ethylmaleimide sensitive factor

SM protein

Sec1/Munc18 protein


Soluble NSF attachment protein


Synaptosomal associated protein of 25 kDa


SNAP receptor


Trimethylamine N-oxide


Total correlation spectroscopy


Transverse relaxation optimized spectroscopy


Vesicle associated membrane protein



We thank Josep Ubach, Imma Fernandez and Iryna Huryeva for preparation of recombinant proteins, Lewis Kay for providing all pulse sequences used in this study, and Thomas Südhof for fruitful discussions. This work was supported by grant I-1304 from the Welch Foundation and NIH grant NS37200 (to J.R.).


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Xiaocheng Chen
    • 1
  • Jun Lu
    • 1
    • 2
  • Irina Dulubova
    • 1
    • 3
  • Josep Rizo
    • 1
  1. 1.Departments of Biochemistry and PharmacologyUniversity of Texas Southwestern Medical CenterDallasUSA
  2. 2.Merck & C. Inc.RahwayUSA
  3. 3.Reata PharmaceuticalsIrvingUSA

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