Preliminary X-ray diffraction analysis of crystals of Bacillus thuringiensis toxin, a cell membrane disrupting protein

Crystals suitable for high resolution X-ray diffraction analysis have been reproducibly grown of the 24,000 M r protein insect toxin from Bacillus thuringiensis. This protein, which demonstrates substantial insecticidal activity by inserting into phospholipid membranes, crystallizes as long square needles from polyethylene glycol 4000 at neutral pH. The crystals are of space group P4 1 and have cell dimensions of a = b = 33 A ̊ and c = 235 A ̊ , which suggests to us a predominantly helical motif for the protein's structure.