Genomic organization of the KTX2 gene, encoding a 'short' scorpion toxin active on K+ channels.

A single intron of 87 bp, close to the region encoding the C-terminal part of the signal peptide, was found in the gene of the 'short' scorpion toxin kaliotoxin 2 of Androctonus australis acting on various types of K+ channels. Its A+T content was particularly high (up to 86%). By walking and ligation-mediated PCR, the promoter sequences of the kaliotoxin 2 gene of Androctonus australis were studied. The transcription unit of the gene is 390 bp long. Consensus sequences were identified. The genes of 'short' scorpion toxins active on K+ channels are organized similarly to those of the 'long' scorpion toxins active on Na+ channels and not like those of structurally related insect defensins, which are intronless.