Genomic organization of three neurotoxins active on small conductance Ca2+-activated potassium channels from the scorpion Buthus martensi Karsch

According to the known primary sequences of three neurotoxins active on sma ll conductance Ca2+-activated potassium channels from the scorpion Buthus m artensi Karsch, their corresponding cDNAs mere cloned and sequenced using 3 '- and 5'-RACE. All of them encoded a signal peptide composed of 28 residue s and a mature toxin of 29, 28 and 33 residues, respectively. Their cDNA de duced sequences mere totally consistent with those determined, and the C-te rminal amidation of one neurotoxin mas confirmed. The genomic DNAs of these three toxins mere also amplified by PCR, cloned and sequenced. They all co nsisted of two exons disrupted by a small single intron, All of these intro ns were inserted within the signal peptide at the same -10 position upstrea m from the mature toxin, consisting of 94, 78 and 87 bp, respectively. (C) 1999 Federation of European Biochemical Societies.