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Synthesis and Structure Determination of µ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities
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Synthesis and Structure Determination of µ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities

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Synthesis, bioactivity, and cloning of the L-type calcium channel blocker omega-conotoxin TxVII

T Sasaki1, Z P Feng, R Scott

  • 1Mitsubishi Kasei Institute of Life Sciences, 11 Minamiooya, Machida-shi, Tokyo 194-8511, Japan.

Biochemistry
|October 3, 1999
PubMed

Insights

Omega-conotoxin TxVII, a novel L-type calcium channel blocker, was synthesized and structurally characterized. This conotoxin exhibits unique properties and specific targeting, highlighting the versatility of conotoxin scaffolds.

Area of Science:

  • * Neuroscience and Pharmacology
  • * Peptide Chemistry and Structural Biology

Background:

  • * Omega-conotoxins are known calcium channel blockers, but TxVII is the first reported to target L-type currents.
  • * TxVII possesses a unique sequence with a net negative charge and high hydrophobicity, differing from other omega-conotoxins while retaining the conserved cysteine framework.

Purpose of the Study:

  • * To synthesize omega-conotoxin TxVII and determine its disulfide bond pairings for structural insights.
  • * To investigate the biological function of TxVII, including its effects on voltage-dependent calcium currents and synaptic transmission.
  • * To explore the specificity of TxVII's interaction with L-type calcium channels.

Main Methods:

  • * Chemical synthesis of TxVII and optimization of air oxidation conditions for proper folding.
  • * Determination of disulfide bond pairings using enzymatic fragmentation and chemical synthesis.
  • * Assessment of TxVII's biological activity on cultured Lymnaea RPeD1 neurons and PC12 cells.

Main Results:

  • * Optimized folding conditions using a cationic buffer and hydrophobic solvent facilitated TxVII synthesis.
  • * Synthetic TxVII suppressed slowly inactivating voltage-dependent calcium currents and synaptic transmission in Lymnaea neurons.
  • * TxVII did not block L-type calcium channels in PC12 cells, indicating potential phyletic or subtype specificity.
  • * Disulfide bond analysis revealed TxVII shares the same pattern as other omega-conotoxins, and its CD spectrum is similar to MVIIA and MVIIC.

Conclusions:

  • * TxVII is a structurally conserved omega-conotoxin that specifically blocks L-type calcium currents and synaptic transmission.
  • * The study highlights the evolutionary versatility of the conotoxin scaffold, enabling the targeting of different ion channels.
  • * TxVII's unique properties and specificity offer potential for further research in neuropharmacology.

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