Crystallization and preliminary X-ray analyses of insect neurotoxins with analgesic effect from the scorpion Buthus martensii Karsch

Three insect neurotoxins from the scorpion Buthus martensii Karsch, named BmK I1, BmK I4 and BmK I6, have been purified and crystallized. BmK I1 and BmK I4 show strong toxicity to insects, while BmK I6 is relatively weaker. They all exhibit an evident analgesic effect on mice; this is a novel biological function for scorpion insect toxins. Their crystals diffract to at least 3.5 (BmK I1), 2.8 (BmK I4), 2.8 (BmK I6 crystal form I) and 2.2 Å (of BmK I6 crystal form II) resolution on an ordinary X-ray source. Crystals of BmK I1 belong to space group P6, with unit-cell parameters a = b = 66.2, c = 176.7 Å. BmK I4 crystallized in the tetragonal space group I4, with unit-cell parameters a = b = 134.5, c = 60.6 Å. BmK I6 has been crystallized in two forms: form I belongs to space group C2, with unit-cell parameters a = 46.5, b = 85.2, c = 32.6 Å, β = 110.5°; form II belongs to space group R3, with the hexagonal unit-cell parameters a = b = 44.5, c = 164.7 Å.