Crystal structure of the receptor binding domain of the botulinum C-D mosaic neurotoxin reveals potential roles of lysines 1118 and 1136 in membrane interactions

► Crystal structure of botulinum C-D mosaic neurotoxin at 1.56 Å resolution. ► BoNT/CD-HCR binds PE liposomes more tightly than BoNT/D-HCR. ► Lysine-1118 may enhance BoNT/CD-HCR synaptosome binding by stabilizing a putative membrane interaction loop. ► Binding of a sulfate ion to K1136 may reflect natural interactions of BoNT/CD-HCR with membrane phospholipids or glycolipids.