Osu1 Toxin

Overview

Osu1 Toxin is a research-grade protein/peptide reagent used in research settings. It is commonly applied as a tool reagent related to Kv1.5 channels biology and/or assay development. It is supplied in Lyophilized format to support flexible downstream use in RUO workflows. Researchers commonly pair it with applications such as Electrophysiology.

Key elements and design rationale

• Molecular identity: MW: 7477.7 Da, Formula: C332H487N101O83S8.
• Source / origin: Oculicosa supermirabilis (Central Asian wolf-spider).
• Quality attributes: Purity: ≥ 97% (HPLC); Bioassay tested: Yes; Sterile / endotoxin-free: No.

Modifications

Disulfide bonds between: Cys10-Cys26, Cys28-Cys40, Cys17-Cys42, Cys19-Cys56

When used as a biochemical or pharmacological tool, results are best interpreted relative to the experimental system (species, expression level, and assay readout) and with appropriate negative and competition-style controls where relevant. This product is intended for research use only.

Biological background

Kappa-lycotoxin-Os1a (Osu1 Toxin) is a 64-amino acid peptidyl toxin derived from the venom of the spider Oculicosa supermirabilis1. Osu1 exhibits inhibitory activity at the hKv1.5 channel and slows the activation kinetics of the Kv1.5 current at ~µM peptide concentration. The mode of action of Osu1 toxin involves binding to the voltage-sensing domain of the hKv1.5 potassium channel rather than occluding its pore. This binding effectively prevents the channel's opening at physiological membrane potentials, resulting in the inhibition of the ultra-rapid delayed rectifier potassium current (IKur). Consequently, this prolongs atrial action potentials, potentially leading to the termination of atrial fibrillation (AF)1,2. The hKv1.5 channel is selectively expressed in human atrial myocytes and is absent in ventricular tissues, reducing the likelihood of ventricular side effects. Osu1 toxin demonstrates a high affinity for hKv1.5, and this specificity makes it a promising candidate for selective AF therapies1,2. The potential applications of Osu1 toxin extend beyond AF. Its unique properties make it a valuable tool for studying ion channel physiology and hold promise for the development of toxin-based therapeutics. Osu1's ability to prolong atrial action potentials without affecting ventricular tissues further highlights its therapeutic relevance1,2.

Research relevance and current trends

• Using high-specificity ligands, toxins, and engineered peptides to dissect closely related receptor/channel subtypes and signaling microdomains.
• Pairing labeled (e.g., fluorescent) proteins/peptides with advanced imaging to map surface expression, trafficking, and nanoscale organization.
• Increasing emphasis on reproducibility through standardized characterization (identity, purity, and lot QC) and transparent reporting of reagent attributes.

Common research applications

• Electrophysiology: commonly used to compare signal, binding, or functional readouts across conditions without implying a specific protocol.

Across these use cases, changes in signal or functional readout are generally interpreted as evidence of differences in target abundance, accessibility, or engagement, but alternative explanations (matrix effects, off-target interactions, or assay artifacts) should be considered.

Notes for experimental interpretation

• Assay context matters: binding assays, functional modulation, and detection workflows can yield different readouts even for the same target system.
• Target complexity: closely related family members, splice variants, and post-translational modifications can influence apparent specificity and potency.
• Matrix and sample effects: buffer composition, detergents, and biological matrices may alter stability or apparent activity; interpret with appropriate controls.
• Control concepts: include negative controls and orthogonal validation (e.g., genetic perturbation or alternative reagents) to support robust interpretation.

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