Steve Ealick's Research Group

Scorpion Toxin Variant-3 (from Centruroides sculpturatus Ewing)

PDB file: 2SN3


Scorpion venoms contain small basic proteins that are responsible for their neurotoxic activities. The crystal structure of the variant-3 protein neurotoxin from the scorpion Centruroides sculpturatus Ewing has been refined at 1.2 Å resolution using restrained least-squares. The final model includes 492 non-hydrogen protein atoms, 453 protein hydrogen atoms, eight 2-methyl-2,4-pentanediol (MPD) solvent atoms, and 125 water oxygen atoms. A molecule of MPD bridges neighboring protein molecules in the crystal lattice, and both MPD enantiomers are present in the crystal.

The scorpion venom proteins are classified in α- and β-types depending on their properties and bonding. The variant-3 neurotoxin from the scorpion Centruroides sculpturatus Ewing consists of a single polypeptide chain of 65 amino acids cross-linked by four disulfide bridges. The molecule has one β-sheet and one α-helix. The β-sheet consists of three antiparallel strands with a left-handed twist. The α-helix runs roughly parallel to the β-sheet. The presence of the four disulfide bonds makes this small molecule very stable. Note also the presence of MPD, the precipitating agent used to grow the crystals, shown with ball-and-stick in the model.

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Zhao B, Carson M, Ealick SE, Bugg CE. Structure of Scorpion Toxin Variant-3 at 1.2 Å Resolution. J. Mol. Biol. 227:239-252 (1992).

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