Structural and mutational analyses of the receptor binding domain of botulinum D/C mosaic neurotoxin: Insight into the ganglioside binding mechanism

► We determined the crystal structure of the receptor binding domain of BoNT in complex with 3′-sialyllactose. ► An electron density derived from the 3′-sialyllactose was confirmed at the cleft in the C-terminal subdomain. ► Alanine site-directed mutagenesis showed that GBS and GBL are important for ganglioside binding. ► A cell binding mechanism, which involves cooperative contribution of two sites, was proposed.