MOLECULAR ANALYSIS OF CDNA AND THE TRANSCRIPT ENCODING THE DEPRESSANTINSECT SELECTIVE NEUROTOXIN OF THE SCORPION LEIURUS-QUINQUESTRIATUS-HEBRAEUS

Analysis of mRNA transcribed off the gene encoding the depressant inse ct selective neurotoxin (LqhIT2) of the scorpion Leiurus quinquestriat us hebraeus revealed a transcript about 400 nucleotides long and two p utative precursors of about 4.4 and 3.5 kb long. Poly(A)+ RNA, purifie d from the venom-gland segments of the scorpion, was reverse transcrib ed into cDNA and a cDNA library was constructed. Two closely related c DNA clones were isolated from the library by probing with a partial cD NA clone encoding the depressant insect toxin of the scorpion Buthotus judaicus. Sequence analysis of the two LqhIT2 cDNA clones revealed an identical 63 bp leader sequence, a 183 bp sequence encoding the matur e polypeptide, and 9 bp encoding Gly-Lys-Lys prior to the termination codon. The two clones are distinguished by a single base substitution at the codon corresponding to amino acid residue 16 of the mature toxi n, and at the non-coding region preceding the poly(A) tail. These find ings elucidate the processing steps in the maturation of LqhIT2 and in dicate genetic polymorphism among the genes encoding this toxin.