Masuyer, GeoffreyZhang, SicaiBarkho, SulymanShen, YiHenriksson, LindaKošenina, SaraDong, MinStenmark, Pål2018-04-192018Masuyer, Geoffrey, Sicai Zhang, Sulyman Barkho, Yi Shen, Linda Henriksson, Sara Košenina, Min Dong, and Pål Stenmark. 2018. “Structural characterisation of the catalytic domain of botulinum neurotoxin X - high activity and unique substrate specificity.” Scientific Reports 8 (1): 4518. doi:10.1038/s41598-018-22842-4. http://dx.doi.org/10.1038/s41598-018-22842-4.http://nrs.harvard.edu/urn-3:HUL.InstRepos:35982063Botulinum neurotoxins (BoNTs) are among the most potent toxins known and are also used to treat an increasing number of medical disorders. There are seven well-established serotypes (BoNT/A-G), which all act as zinc-dependent endopeptidases targeting specific members of the SNARE proteins required for synaptic vesicle exocytosis in neurons. A new toxin serotype, BoNT/X, was recently identified. It cleaves not only the canonical targets, vesicle associated membrane proteins (VAMP) 1/2/3 at a unique site, but also has the unique ability to cleave VAMP4/5 and Ykt6. Here we report the 1.35 Å X-ray crystal structure of the light chain of BoNT/X (LC/X). LC/X shares the core fold common to all other BoNTs, demonstrating that LC/X is a bona fide member of BoNT-LCs. We found that access to the catalytic pocket of LC/X is more restricted, and the regions lining the catalytic pocket are not conserved compared to other BoNTs. Kinetic studies revealed that LC/X cleaves VAMP1 with a ten times higher efficiency than BoNT/B and the tetanus neurotoxin. The structural information provides a molecular basis to understand the convergence/divergence between BoNT/X and other BoNTs, to develop effective LC inhibitors, and to engineer new scientific tools and therapeutic toxins targeting distinct SNARE proteins in cells.en-USJournal Article2018-04-1910.1038/s41598-018-22842-4