Beltless Translocation Domain of Botulinum Neurotoxin A Embodies a Minimum Ion-conductive Channel
| Autor: | Shilpa Sambashivan, Mauricio Montal, Axel T. Brunger, Audrey Fischer |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Botulinum Neurotoxin
Stereochemistry Endocytic cycle Protein domain Membrane Reconstitution Peptide Mapping Biochemistry Ion Channels Protein Structure Secondary Cell Line Protein Translocases 03 medical and health sciences 0302 clinical medicine Protein Domains Humans Neurotoxin Botulinum Toxins Type A Molecular Biology Protein secondary structure Ion channel 030304 developmental biology 0303 health sciences Transmembrane channels Protein Translocation Membranes biology Patch Clamp Chemistry Proton-Motive Force Membrane Proteins Botulism Cell Biology equipment and supplies Single Channels Transmembrane protein Protein Structure Tertiary Chaperone (protein) Biophysics biology.protein human activities 030217 neurology & neurosurgery Molecular Chaperones Reports |
| Zdroj: | The Journal of Biological Chemistry |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.c111.319400 |
| Popis: | Background: A key step in intoxication by botulinum neurotoxins is the translocation of the protease domain by the translocation domain (TD) across endosomes. The requirements for translocation remain poorly understood. Results: A construct encompassing the TD yet devoid of the belt embodies a minimum channel-forming unit. Conclusion: The belt is dispensable for channel formation. Significance: The belt restricts cargo dissociation from channel during translocation. Botulinum neurotoxin, the causative agent of the paralytic disease botulism, is an endopeptidase composed of a catalytic domain (or light chain (LC)) and a heavy chain (HC) encompassing the translocation domain (TD) and receptor-binding domain. Upon receptor-mediated endocytosis, the LC and TD are proposed to undergo conformational changes in the acidic endocytic environment resulting in the formation of an LC protein-conducting TD channel. The mechanism of channel formation and the conformational changes in the toxin upon acidification are important but less well understood aspects of botulinum neurotoxin intoxication. Here, we have identified a minimum channel-forming truncation of the TD, the “beltless” TD, that forms transmembrane channels with ion conduction properties similar to those of the full-length TD. At variance with the holotoxin and the HC, channel formation for both the TD and the beltless TD occurs independent of a transmembrane pH gradient. Furthermore, acidification in solution induces moderate secondary structure changes. The subtle nature of the conformational changes evoked by acidification on the TD suggests that, in the context of the holotoxin, larger structural rearrangements and LC unfolding occur preceding or concurrent to channel formation. This notion is consistent with the hypothesis that although each domain of the holotoxin functions individually, each domain serves as a chaperone for the others. |
| Databáze: | OpenAIRE |
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