Purification, crystallization and preliminary X-ray analysis of an HA17–HA70 (HA2–HA3) complex from Clostridium botulinum type C progenitor toxin

The haemagglutinin (HA) complex of Clostridium botulinum type C toxin is composed of three types of subcomponents: HA33, HA17 and HA70 (also known as HA1, HA2 and HA3, respectively). Here, a 260 kDa HA17–HA70 complex was crystallized. His-tagged HA17 and maltose-binding-protein-tagged HA70 were expressed in Escherichia coli and their complex was affinity-purified using a combination of amylose resin chromatography and nickel–nitrilotriacetic acid agarose chromatography. Diffraction data were collected to 8.0 Å resolution and the crystal belonged to the tetragonal space group P4₁2₁2. The molecular-replacement solution indicated that one molecule of HA17 was bound to each HA70 monomer.