Steve Ealick's Research Group
Scorpion Protein Toxin (Variant-2)
1JZA (space group P3221)
Variant-2 scorpion toxin from Centruroides sculpturatus Ewing (CSE-v2) is a 66-amino acid protein, which was grown using seeding techniques. As in most scorpion toxins, the structure is stabilized by four disulfide bridges. The crystals display a temperature-dependent, reversible phase transition near room temperature. At room temperature, the space group is P3221 with a = 48.8 Å and c = 43.7 Å, and with one molecule per asymmetric unit. Below 4°C the crystals change to P3121 with two molecules in the asymmetric unit. At the lower temperature, a remains the same, but there is an approximate doubling of the c axis but with c' (approximately equal to 2c) = 87.2 Å.
CsE-v2 is a compact globular protein with approximate dimensions of 25 x 32 x 36 Å). CsE-v2 contains one α-helix and a three-stranded antiparallel β-sheet. The α-helix is connected to the middle strand of the β-sheet by a pair of disulfide bonds. The longer outer strand of the β-sheet is linked to the long loop prior to the α-helix by another disulfide bond. The fourth disulfide bond limits the flexibility of the C-terminus.
Cook WJ, Zell A, Watt DD, and Ealick SE. Structure of Variant 2 Scorpion Toxin From Centruroides sculpturatus Ewing. Protein Science 11:479-486 (2002).
Ealick SE, Cook WJ, Fontecilla-Camps JC, Suddath FL, Bugg CE, and Watt DD. Preliminary X-ray Investigation of Variant-2 Scorpion Toxin from Centruroides sculpturatus Ewing: Evidence of a Reversible Transition Between Crystal Forms. J. Biol. Chem. 269(19):12081-12083 (1984).