US Government As Represented by the Secretary of the Army

Melody Jensen

Leonard A Smith

The present invention relates to the construction, expression, and purification of synthetic or recombinant light chain (LC) botulinum neurotoxin genes from all botulinum neurotoxin serotypes. The methods of the invention can provide 1.1 g of the LC per liter of culture. The LC product is stable and proteolytically active. Methods of using the products of the invention are described.

Recombinant light chains of botulinum neurotoxins and light chain fusion proteins for use in research and clinical therapy

neurotoxins, the most potent of all toxins, induce lethal neuromuscular paralysis by inhibiting exocytosis at the neuromuscular junction. The light chains (LC) of these dichain neurotoxins are a new class of zinc-endopeptidases that specifically cleave the synaptosomal proteins, SNAP-25, VAMP, or syntaxin at discrete sites. The present invention relates to the construction, expression, purification, and use of synthetic or recombinantneutoroxin genes. For example, a synthetic gene for the LC of theneurotoxin serotype A (BoNT/A) was constructed and overexpressed in. The gene product was purified from inclusion bodies. The methods of the invention can provide 1.1 g of the LC per liter of culture. The LC product was stable in solution at 4&#xb0; C. for at least 6 months. This rBoNT/A LC was proteolytically active, specifically cleaving the Glu-Arg bond in a 17-residue synthetic peptide of SNAP-25, the reported cleavage site of BoNT/A. Its calculated catalytic efficiency k/Kwas higher than that reported for the native BoNT/A dichain. Treating the rBoNT/A LC with mercuric compounds completely abolished its activity, most probably by modifying the cysteine-164 residue located in the vicinity of the active site. About 70% activity of the LC was restored by adding Znto a Zn-free, apo-LC preparation. The LC was nontoxic to mice and failed to elicit neutralizing epitope(s) when the animals were vaccinated with this protein. In addition, injecting rBoNT/A LC into sea urchin eggs inhibited exocytosis-dependent plasma membrane resealing.

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Frederick, MD, United States of America

Melody Jensen