Carbohydrate recognition mechanism of HA70 from Clostridium botulinum deduced from X-ray structures in complexes with sialylated oligosaccharides.

Clostridium botulinum produces the botulinum neurotoxin, forming a large complex as progenitor toxins in association with non-toxic non-hemagglutinin and/or several different hemagglutinin (HA) subcomponents, HA33, HA17 and HA70, which bind to carbohydrate of glycoproteins from epithelial cells in the infection process. To elucidate the carbohydrate recognition mechanism of HA70, X-ray structures of HA70 from type C toxin (HA70/C) in complexes with sialylated oligosaccharides were determined, and a binding assay by the glycoconjugate microarray was performed. These results suggested that HA70/C can recognize both α2-3- and α2-6-sialylated oligosaccharides, and that it has a higher affinity for α2-3-sialylated oligosaccharides.