6F4E:
reference: Structural characterisation of the catalytic domain of botulinum neurotoxin X - high activity and unique substrate specificity., Masuyer G, Zhang S, Barkho S, Shen Y, Henriksson L, Kosenina S, Dong M, Stenmark P, Sci Rep. 2018 Mar 14;8(1):4518. doi: 10.1038/s41598-018-22842-4. PMID: 29540745

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