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Crystal Structure of Variant 2 Scorpion Toxin from Centruroides sculpturatus Ewing
Structural highlights
FunctionSCX2_CENSC Beta toxins bind voltage-independently at site-4 of sodium channels (Nav) and shift the voltage of activation toward more negative potentials thereby affecting sodium channel activation and promoting spontaneous and repetitive firing (By similarity). Induces immediate paralysis in crickets after injection, with a total paralysis occurring within 15-30 minutes and lasting for 1-2 hours. Is also lethal to vertebrate (chicks) when injected in very high dosages (more that 100 mg/kg).[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCentruroides sculpturatus Ewing variant 2 toxin (CsE-v2) is a neurotoxin isolated from the venom of a scorpion native to the Arizona desert. The structure of CsE-v2 was solved in two different crystal forms using a combination of molecular replacement and multiple isomorphous replacement techniques. Crystals of CsE-v2 display a temperature-dependent, reversible-phase transition near room temperature. At lower temperature the space group changes from P3(2)21 to P3(1)21 with an approximate doubling of the C-axis. The small-cell structure, which has one molecule per asymmetric unit, has an R factor of 0.229 at 2.8 A resolution. The large-cell structure has two molecules per asymmetric unit and was refined at 2.2 A resolution to an R factor of 0.255. CsE-v2 is a rigid, compact structure with four intrachain disulfide bonds. The structure is similar to other long-chain beta neurotoxins, and the largest differences occur in the last six residues. The high-resolution structure of CsE-v2 corrects an error in the reported C-terminal sequence; the terminal tripeptide sequence is Ser 64-Cys 65-Ser 66 rather than Ser 64-Ser 65-Cys 66. Comparison of CsE-v2 with long-chain alpha toxins reveals four insertions and one deletion, as well as additional residues at the N and C termini. Structural alignment of alpha and beta toxins suggests that the primary distinguishing feature between the two classes is the length of the loop between the second and third strands in a three-strand beta sheet. The shorter loop in alpha toxins exposes a critical lysine side chain, whereas the longer loop in beta toxins buries the corresponding basic residue (either arginine or lysine). Structure of variant 2 scorpion toxin from Centruroides sculpturatus Ewing.,Cook WJ, Zell A, Watt DD, Ealick SE Protein Sci. 2002 Mar;11(3):479-86. PMID:11847271[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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