Crystallization and preliminary X-ray analysis of a novel haemagglutinin component of the toxin complex of serotype C Clostridium botulinum

The botulinum toxin complex, the causative agent of botulism, passes through the intestinal wall via sugar-chain-dependent cell binding of a haemagglutinin of 33 kDa molecular weight (HA-33). The amino-acid sequence of the C-terminal half of HA-33 of the serotype C strain Yoichi (C-Yoichi) shares only 46% identity with those of the major serotype C strains. Additionally, C-Yoichi HA-­33 exhibits a unique sugar-binding specificity. In the present work, C-Yoichi HA-33 was expressed in Escherichia coli and crystallized. Diffraction data were collected at a resolution of 2.2 Å. The crystals belonged to space group R3. The complete detailed protein structure will yield insight into how the unique HA-33 protein recognizes sugar moieties.