Crystallization and preliminary x-ray investigation of a protein neurotoxin from the sea anemone Anthopleura xanthogrammica.

Neurotoxic protein AX-I isolated from the sea anemone Anthopleura xanthogrammica has been crystallized. Two crystal forms were obtained. One form is tetragonal, space group P41 or P43 , with cell dimensions a = b = 40.74(2) A and c = 34.13(3) A. The second crystal form is hexagonal, space group P622 , with cell dimensions a = b = 72.23(2) A and c = 39.16(2)A. Density measurements indicate that the tetragonal crystals contain one toxin molecule/asymmetric unit. Both crystal forms diffract to high resolution.