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Screening and cDNA cloning of Kv1 potassium channel toxins in sea anemones.

Yamaguchi Y, Hasegawa Y, Honma T, Nagashima Y, Shiomi K - Mar Drugs (2010)

Bottom Line: When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of (125)I-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.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 κ(1.3)-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34-63% identities with the other type 1 potassium channel toxins.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Konan-4, Minato-ku, Tokyo, Japan.

ABSTRACT
When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of (125)I-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 κ(1.3)-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34-63% identities with the other type 1 potassium channel toxins.

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Amino acid sequences of type 1 potassium channel peptide toxins from sea anemones. The residues identical with those of κ1.3-SHTX-Sg1a are shown in red. Asterisks under the sequence of κ1.3-ATTX-Bg1a represent the dyad (Lys-Tyr) that is crucial for the binding to potassium channels.
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f3-marinedrugs-08-02893: Amino acid sequences of type 1 potassium channel peptide toxins from sea anemones. The residues identical with those of κ1.3-SHTX-Sg1a are shown in red. Asterisks under the sequence of κ1.3-ATTX-Bg1a represent the dyad (Lys-Tyr) that is crucial for the binding to potassium channels.

Mentions: The amino acid sequences of the mature portions of the six potassium channel toxins are shown in Figure 3, together with those of the known type 1 potassium channel toxins. Each of the six toxins has six Cys residues in the same positions as the known type 1 toxins, suggesting that the three disulfide bridges are located between 3Cys and 35Cys, between 12Cys and 28Cys and between 17Cys and 32Cys as demonstrated for κ1.3-SHTX-Hm1a [15], κ1.3-SHTX-She1a [28] and κ1.3-ATTX-Bg1a [14]. In addition, the dyad (Lys-Tyr), which is assumed to be crucial for the toxin binding to potassium channels [29–32], is conserved in the six toxins, as in the known type 1 toxins. Interestingly, although the six toxins include three toxins (κ1.3-SHTX-Sg1a, κ1.3-SHTX-Sha1a and κ1.3-SHTX-Sm1a) from Stichodactyla species of Stichodactylidae and three toxins (κ1.3-TLTX-Ca1a, κ1.3-TLTX-Hh1a and κ1.3-TLTX-Ta1a) from Thalassianthidae species, they share more than 90% sequence identity with one another and also with κ1.3-SHTX-She1a; even the same sequence is seen between κ1.3-SHTX-Sg1a and κ1.3-SHTX-Sha1a, between κ1.3-SHTX-Sm1a and κ1.3-SHTX-She1a and between κ1.3-TLTX-Hh1a and κ1.3-TLTX-Ta1a. In contrast, the six toxins show rather low sequence identities (34–63%) with κ1.3-SHTX-Hm1a, κ1.3-ATTX-Aeq1a, κ1.3-ATTX-Aer1a, κ1.3-ATTX-As1a and κ1.3-ATTX-Bg1a.


Screening and cDNA cloning of Kv1 potassium channel toxins in sea anemones.

Yamaguchi Y, Hasegawa Y, Honma T, Nagashima Y, Shiomi K - Mar Drugs (2010)

Amino acid sequences of type 1 potassium channel peptide toxins from sea anemones. The residues identical with those of κ1.3-SHTX-Sg1a are shown in red. Asterisks under the sequence of κ1.3-ATTX-Bg1a represent the dyad (Lys-Tyr) that is crucial for the binding to potassium channels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3039155&req=5

f3-marinedrugs-08-02893: Amino acid sequences of type 1 potassium channel peptide toxins from sea anemones. The residues identical with those of κ1.3-SHTX-Sg1a are shown in red. Asterisks under the sequence of κ1.3-ATTX-Bg1a represent the dyad (Lys-Tyr) that is crucial for the binding to potassium channels.
Mentions: The amino acid sequences of the mature portions of the six potassium channel toxins are shown in Figure 3, together with those of the known type 1 potassium channel toxins. Each of the six toxins has six Cys residues in the same positions as the known type 1 toxins, suggesting that the three disulfide bridges are located between 3Cys and 35Cys, between 12Cys and 28Cys and between 17Cys and 32Cys as demonstrated for κ1.3-SHTX-Hm1a [15], κ1.3-SHTX-She1a [28] and κ1.3-ATTX-Bg1a [14]. In addition, the dyad (Lys-Tyr), which is assumed to be crucial for the toxin binding to potassium channels [29–32], is conserved in the six toxins, as in the known type 1 toxins. Interestingly, although the six toxins include three toxins (κ1.3-SHTX-Sg1a, κ1.3-SHTX-Sha1a and κ1.3-SHTX-Sm1a) from Stichodactyla species of Stichodactylidae and three toxins (κ1.3-TLTX-Ca1a, κ1.3-TLTX-Hh1a and κ1.3-TLTX-Ta1a) from Thalassianthidae species, they share more than 90% sequence identity with one another and also with κ1.3-SHTX-She1a; even the same sequence is seen between κ1.3-SHTX-Sg1a and κ1.3-SHTX-Sha1a, between κ1.3-SHTX-Sm1a and κ1.3-SHTX-She1a and between κ1.3-TLTX-Hh1a and κ1.3-TLTX-Ta1a. In contrast, the six toxins show rather low sequence identities (34–63%) with κ1.3-SHTX-Hm1a, κ1.3-ATTX-Aeq1a, κ1.3-ATTX-Aer1a, κ1.3-ATTX-As1a and κ1.3-ATTX-Bg1a.

Bottom Line: When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of (125)I-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.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 κ(1.3)-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34-63% identities with the other type 1 potassium channel toxins.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Konan-4, Minato-ku, Tokyo, Japan.

ABSTRACT
When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of (125)I-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 κ(1.3)-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34-63% identities with the other type 1 potassium channel toxins.

Show MeSH