Purification, crystallization and preliminary X-ray crystallographic analysis of agkaggregin, a C-type lectin-like protein from Agkistrodon acutus venom

A snake-venom C-type lectin-like protein, agkaggregin, has been isolated from Agkistrodon acutus venom. Agkaggregin has an apparent molecular mass of about 28 kDa and consists of two different types of subunits, an α-subunit (∼15 kDa) and a β-subunit (∼14 kDa). Agkaggregin has the ability to induce platelet aggregation at concentrations of the order of nanomoles. The agkaggregin crystals grew for nearly a year by hanging-drop vapour diffusion and belong to the I222 space group, with unit-cell parameters a = 64.75, b = 74.21, c = 133.24 Å. One asymmetric unit contains one αβ heterodimer, corresponding to a volume-to-mass ratio of 2.795 ų Da⁻¹. Agkaggregin may exist in two association forms: an αβ heterodimer and a dimer of αβ heterodimers that associates during the long process of crystallization.