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Translocation of botulinum neurotoxin light chain protease through the heavy chain channel

Nature Structural Biology volume 10, pages 13–18 (2003)Cite this article

Abstract

Clostridial botulinum neurotoxins (BoNTs) abort the process of neurotransmitter release at presynaptic motor nerve terminals, causing muscle paralysis. An enigmatic step in the intoxication process is the mechanism by which the neurotoxin heavy chain (HC) forms the conduit for the translocation of the light chain (LC) protease across the endosomal membrane into the cytosol, its site of action. Here we investigate the mechanism of LC translocation by using the combined detection of channel currents and substrate proteolysis, the two hallmark activities of BoNT. Our data are consistent with the translocation of the LC through the HC channel and show that the LC protease activity is retrieved in the trans compartment after translocation. We propose that the BoNT HC–LC complex embedded in the membrane is a transmembrane chaperone, a dynamic structural device that prevents aggregation and achieves translocation of the LC. In this regard, the complex is similar to the protein conducting/translocating channels of the endoplasmic reticulum, mitochondria and chloroplasts.

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Figure 1: Channel formation by BoNT A and HC A in lipid bilayers.
Figure 2: Blocking of HC A channels by the LC A.
Figure 3: Detection of the endopeptidase activity of translocated LC A in bilayer experiments.
Figure 4: BoNT A endopeptidase activity correlates with BoNT A channel activity and the unfolding of LC A.

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Acknowledgements

We thank M. Goodnough for BoNT A and its individual chains; B.R. Singh and R.C. Stevens for the recombinant clones of BoNT A HC, LC and SNAP-25b; and N. Gude and J. Santos for perceptive comments. The project was supported by the U.S. Army Medical Research and Materiel Command.

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  1. Division of Biological Sciences, Section of Neurobiology, University of California San Diego, 9500 Gilman Drive, La Jolla, 92093-0366, California, USA

    Lilia K. Koriazova & Mauricio Montal

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  1. Lilia K. Koriazova
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  2. Mauricio Montal
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Correspondence to Mauricio Montal.

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Koriazova, L., Montal, M. Translocation of botulinum neurotoxin light chain protease through the heavy chain channel. Nat Struct Mol Biol 10, 13–18 (2003). https://doi.org/10.1038/nsb879

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