Crystal structure of the catalytic domain of the Weissella oryzae botulinum-like toxin

Botulinum neurotoxins (BoNTs) are the most potent toxins known. So far, eight serotypes have been identified that all act as zinc-dependent endopeptidases targeting SNARE proteins and inhibiting the release of neurotransmitters. Recently, the first botulinum toxin-like protein was identified outside the Clostridial genus, designated BoNT/Wo in the genome of Weissella oryzae. Here, we report the 1.6 Å X-ray crystal structure of the light chain of BoNT/Wo (LC/Wo). LC/Wo presents the core fold common to BoNTs but has an unusually wide, open and negatively charged catalytic pocket, with an additional Ca²⁺ ion besides the zinc ion and a unique ß-hairpin motif. The structural information will help establish the substrate profile of BoNT/Wo and help our understanding of how BoNT evolved.