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

Abstract

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 Andvoctonus 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.

Genomic Organization of BmTXKβ and BmTXKS2, Two Scorpion Venom Peptides From Buthus martensii Karsch

“…The coding DNA sequence was completely consistent with its cDNA sequence. The intron had a consensus splice site of GT at the 5 0 -end and AG at the 3 0 -end, and was rich in A C T content around 71% (around 57% in the exons), which was similar with other scorpion toxin genes (11,12,17 )…”

“…In this paper, we described the molecular characterization of the genomic regions of a b -KTx member (BmTXKb ) and an insect defensin-like peptide (BmTXKS2) from BmK. Our results show that genomic organization of BmTXKb and BmTXKS2 are different from that of all other scorpion toxins characterized (11,12). Mature peptide coding region of BmTXKb gene is disrupted by an intron with 886 bp, whereas the intron of BmTXKS2 gene is located within its propeptide coding region.…”

Genomic organization of three novel toxins from the scorpion Buthus martensi Karsch that are active on potassium channels

“…Though over 40 different scorpion K + channel toxins have been reported [22], there has been little information on their gene structures. Only the genes of KTX from Androctonus australis [14], ChTX from Leiurus quinquestriatus hebraeus [16] and toxin Ts κ from Tityus serrulatus (only the cDNA sequence is available) [15] have been elucidated. In our previous paper we described the genomic organization of BmP01, BmP03 and BmP05 acting on smallconductance Ca# + -activated K + channels [13].…”

“…For example, the intron sequence of 87 bp of BmKTX has a similar size and approx. 90 % identity with that of KTX [14] and both of them are voltage-dependent K + -channel toxins, although BmKTX is delivered from the Asian scorpion B. martensi, whereas KTX is from the north African scorpion Androctonus mauretanicus mauretanicus. Considering the wide geographical distribution, this high similarity might imply that these two species of scorpions might have evolved from the same ancestor.…”

“…Here we describe further the cDNA and genomic DNA sequences of BmKTX, BmTX1 and BmTX2, belonging to two further different subgroups. Comparing their gene sequences with other K + -channel toxins [13][14][15][16], it was indicated that despite only low amino acid sequence similarity, their gene organizations and intron features are conserved. In all toxins there are two exons and one intron splitting a codon at a similar location, namely close to the end of the signal peptide.…”