Crystallization and preliminary X-ray diffraction studies of the neurotoxic, heterodimeric phospholipase A2 from the Taiwan viper (Vipera russelli formosensis).

The 28 kDa heterodimeric complex from Taiwan viper (F4/F7 complex) is composed of a neurotoxic phospholipase A2 (F4) and a non-toxic PLA2-like component (F7). Despite a high sequence identity (65%), the biological and pharmacological activities of F4 and F7 are contrasting. The complex is a structural analogue of Vipoxin found in the venom of the Bulgarian viper Vipera ammodites meridionalis. It is unclear how and why such varied bioactivities are expressed in these similar components. The F4/F7 complex has been crystallized using hanging-drop vapour diffusion and macroseeding techniques. The space group is monoclinic P21 with unit-cell dimensions a = 74.92, b = 85.13, c = 78.16 A and beta = 95.12 degrees. X-ray intensity data to 2.0 A resolution have been collected at 120 K and the structure has been solved using the molecular-replacement method. There are four F4/F7 complex molecules in the asymmetric unit, which do not exhibit any local point-group symmetry.