Abstract
When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of 125I-α-dendrotoxin to rat synaptosomal membranes, 11 species (two species of Actiniidae, one species of Hormathiidae, five species of Stichodactylidae and three species of Thalassianthidae) were found to be positive. Furthermore, full-length cDNAs encoding type 1 potassium channel toxins from three species of Stichodactylidae and three species of Thalassianthidae were cloned by a combination of RT-PCR, 3′RACE and 5′RACE. The precursors of these six toxins are commonly composed of signal peptide, propart and mature peptide portions. As for the mature peptide (35 amino acid residues), the six toxins share more than 90% sequence identities with one another and with κ1.3-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34–63% identities with the other type 1 potassium channel toxins.
Highlights
Sea anemones contain various classes of peptide toxins, especially those acting on sodium or potassium channels [1,2,3]
A total of 15 potassium channel toxins isolated so far can be structurally classified into four types [9]: type 1 toxins (35–37 amino acid residues) include κ1.3-ATTX-Aeq1a (AeK; toxin names are described in this paper based on the nomenclature proposed by King et al [10], with their original names at the first appearance) from Actinia equina [11], κ1.3-ATTX-Aer1a (AETX K) from Anemonia erythraea [12], κ1.3-ATTX-As1a (AsKS or kaliseptine) from Anemonia sulcata [13], κ1.3-ATTX-Bg1a (BgK) from Bunodosoma granulifera [14], κ1.3-SHTX-Hm1a (HmK) from Heteractis magnifica [15] and κ1.3-SHTX-She1a (ShK) from
The following 11 species showing more than 50% inhibition were judged to be substantially positive: two species (Macrodactyla doreensis and Telactinia citrina) of the family Actiniidae, one species (Calliactis polypus) of the family Hormathiidae, five species (Heteractis magnifica, Mesactinia ganensis, Stichodactyla haddoni, Stichodactyla mertensii and Stichodactyla tapetum) of the family Stichodactylidae and three species (Cryptodendrum adhaesivum, Heterodactyla hemprichii and Thalassianthus aster) of the family
Summary
Sea anemones contain various classes of peptide toxins, especially those acting on sodium or potassium channels [1,2,3]. The most extensively studied peptide toxins are sodium channel toxins that. Kv1 potassium channel toxins, not isolated, have been detected in three species of sea anemones (Actinia bermudensis, Bunodosoma cangicum and Stichodactyla mertensii) [21]. It should be noted that all the sea anemones that have been shown to contain potassium channel toxins, including Kv1 channel toxins, belong to either the family Actiniidae or the family. In this study screening for Kv1 potassium channel toxins, which was based on the competitive inhibition of the binding of radiolabeled α-dendrotoxin Molecular cloning was attempted to elucidate the primary structures of type 1 potassium channel toxins, for which degenerate primers could be designed from the known nucleotide sequences of the cDNAs encoding κ1.3-ATTX-Aer1a [12] and κ1.3-SHTX-Hm1a [15]
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