Isolation and Characterization of CvIV4: A Pain Inducing α- Scorpion Toxin
CvIV4 (underlined) is aligned with seven toxin sequences from other species. Alignment is based on cysteine residue position (shaded background) and toxins are arranged in order of descending percent identity with respect to CvIV4. Percent identify (%ID) is estimated from the number of amino acids shared by two toxins (NCBI Protein BLAST). While CvIV4 (JF938594) and CeII8 (P0CH40) are structurally similar (64% ID), they are functionally different as CvIV4 is classified as an α-toxin and CeII8 as a β-toxin (classification based on electrophysiological recordings from Na+ channel subtypes). CvIV4 shares over 50% of its amino acid residues with the remaining six toxins. Ts3 (P01496) and TsV (P46115) are classified as α-toxins based on electrophysiological studies of mammalian cells and tissues. Tst3 (P0C8X5), Pg8 (ACD35698), TbTx5 (P0C5K8) and LmNaTx10 (ACD35698) are classifed as α-toxins based solely on sequence similarity. Cv = Centruroides vittatus, Ce = Centruroides elegans, Tst = Tityus stigmurus, Ts = Tityus serrulatus, Pg = Parabuthus granulatus, Tb = Tityus bahaensis, Lm = Lychas mucronatus. GenBank accession numbers are shown in parentheses following the toxin name.