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Studies on sea snake venom.

Tamiya N, Yagi T - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Bottom Line: Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi).The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor.Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence."

View Article: PubMed Central - PubMed

Affiliation: Tohoku University, Miyagi, Japan.

ABSTRACT
Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi). Amino acid sequences of the toxins indicated that the toxins are members of a superfamily consisting of short and long neurotoxins and cytotoxins found in sea snakes and terrestrial snakes. The short neurotoxins to which erabutoxins belong act by blocking the nicotinic acetylcholine receptor on the post synaptic membrane in a manner similar to that of curare. X-ray crystallography and NMR analyses showed that the toxins have a three-finger structure, in which three fingers made of three loops emerging from a dense core make a gently concave surface of the protein. The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor. Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence."

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Effects of Ea and Eb on the contraction of sciatic-nerve-sartorius-muscle preparation of frogs (Rana nigromaculata).4) An isolated sciatic-nerve-sartorius muscle preparation was placed in 4.3 mL of glucose Ringer solution (9.0 g of NaCl, 0.42 g of KCl, 0.24 g of CaCl2, 0.5 g of NaHCO3 and 1.0 g of glucose in 1.4 L of water), which was continuously bubbled with air. The electrical stimulations were given to the preparation either directly to the muscle (DS) or indirectly through the nerve (IS) every 5 s, and the contractions were recorded by a strain-gauze transducer. The solution of Ea (0.1 mL) was added to the medium at the point marked Ea (final concn. 0.11 µg of Kjeldahl nitrogen/mL of Ringer solution) in (a). The recrystallized Eb solution (0.1 mL) was added at the point marked Eb (final concn. 0.12 µg of Kjeldahl nitrogen/mL of Ringer solution) in (b). The muscle was washed with the Ringer solution at the points marked W in (b).
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fig01: Effects of Ea and Eb on the contraction of sciatic-nerve-sartorius-muscle preparation of frogs (Rana nigromaculata).4) An isolated sciatic-nerve-sartorius muscle preparation was placed in 4.3 mL of glucose Ringer solution (9.0 g of NaCl, 0.42 g of KCl, 0.24 g of CaCl2, 0.5 g of NaHCO3 and 1.0 g of glucose in 1.4 L of water), which was continuously bubbled with air. The electrical stimulations were given to the preparation either directly to the muscle (DS) or indirectly through the nerve (IS) every 5 s, and the contractions were recorded by a strain-gauze transducer. The solution of Ea (0.1 mL) was added to the medium at the point marked Ea (final concn. 0.11 µg of Kjeldahl nitrogen/mL of Ringer solution) in (a). The recrystallized Eb solution (0.1 mL) was added at the point marked Eb (final concn. 0.12 µg of Kjeldahl nitrogen/mL of Ringer solution) in (b). The muscle was washed with the Ringer solution at the points marked W in (b).

Mentions: Toxicity of Ea and Eb was demonstrated with isolated frog muscle.4) In the aerated Ringer solution, the contracture of frog (Rana nigromaculata) sciatic-nerve-sartorius-muscle preparation by indirect electric stimuli through the nerve was inhibited, but the contracture by direct stimuli of the muscle was not inhibited (Fig. 1). Acetylcholine-induced contracture of frog rectus abdominal muscle was inhibited by the toxins (Fig. 2). These results clearly demonstrated that the toxins interfered with the binding of acetylcholine to the acetylcholine receptor (AChR) on the post synaptic membrane in a manner similar to that of curare, because they blocked neuromuscular transmission, and inhibited the muscle contraction induced by acetylcholine.4,10) The toxin was suggested to exert toxicity by blocking respiration, because mice injected with lethal amount of the toxin were rescued by artificial respiration.


Studies on sea snake venom.

Tamiya N, Yagi T - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Effects of Ea and Eb on the contraction of sciatic-nerve-sartorius-muscle preparation of frogs (Rana nigromaculata).4) An isolated sciatic-nerve-sartorius muscle preparation was placed in 4.3 mL of glucose Ringer solution (9.0 g of NaCl, 0.42 g of KCl, 0.24 g of CaCl2, 0.5 g of NaHCO3 and 1.0 g of glucose in 1.4 L of water), which was continuously bubbled with air. The electrical stimulations were given to the preparation either directly to the muscle (DS) or indirectly through the nerve (IS) every 5 s, and the contractions were recorded by a strain-gauze transducer. The solution of Ea (0.1 mL) was added to the medium at the point marked Ea (final concn. 0.11 µg of Kjeldahl nitrogen/mL of Ringer solution) in (a). The recrystallized Eb solution (0.1 mL) was added at the point marked Eb (final concn. 0.12 µg of Kjeldahl nitrogen/mL of Ringer solution) in (b). The muscle was washed with the Ringer solution at the points marked W in (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3066545&req=5

fig01: Effects of Ea and Eb on the contraction of sciatic-nerve-sartorius-muscle preparation of frogs (Rana nigromaculata).4) An isolated sciatic-nerve-sartorius muscle preparation was placed in 4.3 mL of glucose Ringer solution (9.0 g of NaCl, 0.42 g of KCl, 0.24 g of CaCl2, 0.5 g of NaHCO3 and 1.0 g of glucose in 1.4 L of water), which was continuously bubbled with air. The electrical stimulations were given to the preparation either directly to the muscle (DS) or indirectly through the nerve (IS) every 5 s, and the contractions were recorded by a strain-gauze transducer. The solution of Ea (0.1 mL) was added to the medium at the point marked Ea (final concn. 0.11 µg of Kjeldahl nitrogen/mL of Ringer solution) in (a). The recrystallized Eb solution (0.1 mL) was added at the point marked Eb (final concn. 0.12 µg of Kjeldahl nitrogen/mL of Ringer solution) in (b). The muscle was washed with the Ringer solution at the points marked W in (b).
Mentions: Toxicity of Ea and Eb was demonstrated with isolated frog muscle.4) In the aerated Ringer solution, the contracture of frog (Rana nigromaculata) sciatic-nerve-sartorius-muscle preparation by indirect electric stimuli through the nerve was inhibited, but the contracture by direct stimuli of the muscle was not inhibited (Fig. 1). Acetylcholine-induced contracture of frog rectus abdominal muscle was inhibited by the toxins (Fig. 2). These results clearly demonstrated that the toxins interfered with the binding of acetylcholine to the acetylcholine receptor (AChR) on the post synaptic membrane in a manner similar to that of curare, because they blocked neuromuscular transmission, and inhibited the muscle contraction induced by acetylcholine.4,10) The toxin was suggested to exert toxicity by blocking respiration, because mice injected with lethal amount of the toxin were rescued by artificial respiration.

Bottom Line: Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi).The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor.Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence."

View Article: PubMed Central - PubMed

Affiliation: Tohoku University, Miyagi, Japan.

ABSTRACT
Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi). Amino acid sequences of the toxins indicated that the toxins are members of a superfamily consisting of short and long neurotoxins and cytotoxins found in sea snakes and terrestrial snakes. The short neurotoxins to which erabutoxins belong act by blocking the nicotinic acetylcholine receptor on the post synaptic membrane in a manner similar to that of curare. X-ray crystallography and NMR analyses showed that the toxins have a three-finger structure, in which three fingers made of three loops emerging from a dense core make a gently concave surface of the protein. The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor. Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence."

Show MeSH
Related in: MedlinePlus