The cDNA sequence of an excitatory insect selective neurotoxin from the scorpion Buthus martensi Karsch

The full-length cDNA of an excitatory insect selective neurotoxin was ampli fied from total cDNAs of venomous glands of the scorpion Buthus martensi Ka rsch (BmK) using the 3'RACE and 5'RACE (rapid amplification of cDNA ends, R ACE) method and sequenced. The cDNA encoded a precursor of the insect toxin of 88 amino acid residues, including a signal peptide of 18 residues and a mature toxin of 70 residues. The cDNA deduced sequence of this toxin was h omologous with the determined amino acid sequence of BmK IT1, an excitatory insect toxin purified from the scorpion venom, except for three different residues, two at the positions 24-25, and another in the COOH-terminus of t he toxin. Among them the COO-terminal residue Gly in the cDNA deduced seque nce was predominantly different from the conserved residue Asn found in oth er known scorpion excitatory insect toxins. (C) 1999 Elsevier Science Ltd. All rights reserved.