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α-Conotoxin SIA is a 13-amino-acid, disulfide-rich peptide originally isolated from the venom of Conus striatus. It belongs to the α3/5 conotoxin family and acts as a competitive antagonist of muscle-type nicotinic acetylcholine receptors (nAChRs). α-Conotoxin SIA is widely used as a pharmacological probe for studying neuromuscular nAChR structure, ligand-binding interfaces, receptor subtype selectivity, and peptide–receptor interactions.
The peptide contains two native disulfide bonds and a C-terminal amide. Its compact disulfide-constrained structure is essential for maintaining the receptor-binding conformation characteristic of α-conotoxins.
α-Conotoxin SIA Product Information
| Property | Information |
|---|---|
| Product Name | α-Conotoxin SIA |
| CAS No. | 135190-31-7 |
| Sequence | YCCHPACGKNFDC-NH₂ |
| Length | 13 amino acids |
| Molecular Formula | C₆₀H₈₂N₁₈O₁₇S₄ |
| Molecular Weight | 1455.7 Da |
| C-Terminus | Amide |
| Disulfide Bonds | Cys2–Cys7; Cys3–Cys13 |
| Cysteine Framework | CC–C–C |
| α-Conotoxin Subclass | α3/5 |
| Natural Source | Conus striatus |
| Primary Target | Muscle-type nicotinic acetylcholine receptors |
| Form | Lyophilized peptide |
| Purity | According to selected product specification |
Product Overview
α-Conotoxin SIA belongs to the classical short α-conotoxin family, whose members contain four cysteine residues forming two disulfide bridges and interact with extracellular ligand-binding sites of nicotinic acetylcholine receptors.
SIA is particularly useful for investigating muscle-type nAChRs. Literature studies demonstrate strong discrimination between receptor-binding interfaces depending on species and receptor composition. SIA, MI, and GI can show pronounced preference for one acetylcholine-binding interface over another, illustrating how small sequence changes within closely related conotoxins can produce substantial changes in receptor selectivity.
Alan Scientific Technical View: α-Conotoxin SIA is an excellent example of why sequence similarity does not necessarily predict identical pharmacology. For conotoxin analog development, receptor subtype, species, disulfide connectivity, and individual loop residues should be considered together.
Biological Activity & Target
α-Conotoxin SIA acts primarily as an antagonist of muscle-type nAChRs. Literature studies have reported nanomolar activity against mammalian muscle receptors, although potency varies substantially according to receptor subtype, species, and experimental system.
| Research Property | Description |
|---|---|
| Primary Target | Muscle-type nAChRs |
| Mechanism | Competitive receptor antagonist |
| Peptide Class | α3/5 α-conotoxin |
| Major Research Use | nAChR pharmacology and receptor-interface studies |
Structural Features
α-Conotoxin SIA has the sequence:
YCCHPACGKNFDC-NH₂
with native disulfide connectivity:
Cys2–Cys7
Cys3–Cys13
This globular disulfide pattern constrains the peptide into the bioactive α-conotoxin fold. Changes in loop residues can significantly alter binding affinity and receptor-interface selectivity even when the cysteine framework remains unchanged.
Research Applications
| Application | Typical Use |
|---|---|
| nAChR Research | Characterization of muscle-type nicotinic receptors |
| Receptor Pharmacology | Comparison of receptor-binding interfaces |
| Electrophysiology | Functional inhibition of nAChR-mediated currents |
| Structure–Activity Studies | Evaluation of α-conotoxin analogs |
| Peptide Engineering | Investigation of loop-residue contributions to selectivity |
Quality Control
Peptide identity and purity are typically evaluated using mass spectrometry (MS) and analytical HPLC, with a Certificate of Analysis provided according to the selected product specification.
For α-Conotoxin SIA, correct C-terminal amidation and native disulfide connectivity should be considered together with chromatographic purity.
Storage & Handling
Follow the batch-specific COA or product storage specification supplied with the peptide. After reconstitution, stability may depend on solvent composition, concentration, pH, and temperature. Minimize unnecessary freeze–thaw cycles.
Selected References
1. Myers RA, et al. α-Conotoxins, small peptide probes of nicotinic acetylcholine receptors. Biochemistry. 1991;30:9370–9377.
Describes purification, sequencing, synthesis, and receptor-probe applications of α-Conotoxin SIA.
2. Groebe DR, et al. α-Conotoxins selectively inhibit one of the two acetylcholine binding sites of nicotinic receptors. Molecular Pharmacology. 1995.
3. Hann RM, et al. The 9-arginine residue of α-Conotoxin GI is responsible for selective high affinity for an acetylcholine receptor agonist site. Biochemistry. 1997. Includes comparative SIA pharmacology.
Related Technical Resources
Peptide Modifications & Applications
Peptide Purification & Quality Control
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