# Follistatin-344

> Recombinant follistatin isoform of 344 residues that binds activin

All products are sold strictly for laboratory research use only. Not for human or veterinary use.

- Web page: https://peptidemedixeu.com/en/products/follistatin-344/
- Brand: Peptide Medix EU
- Category: [IGF & Muscle Peptides](https://peptidemedixeu.com/en/collections/igf-peptides/)
- Purity: ≥98% by HPLC; lot-matched COA available
- CAS number: 80449-31-6
- from €182 (EUR)

## Sizes and prices (EUR)

| Size | Price | SKU |
| --- | --- | --- |
| 1 mg | €182 | FOLLISTATIN-344-1-MG |

_Catalog prices at build time; the web page and checkout are authoritative._

## Specifications

- **CAS number:** 80449-31-6
- **Molecular weight:** 37800 Da (approximately 37.8 kDa)
- **Form:** Lyophilized recombinant protein, sealed glass vial
- **Purity:** ≥98% by HPLC; lot-matched COA available
- **Available sizes:** 1 mg
- **Solubility:** Sterile or bacteriostatic water; carrier protein often added for dilute stocks
- **Storage (lyophilized):** −20 °C, protected from light and moisture
- **Storage (reconstituted):** 2–8 °C for immediate work; aliquot and hold at −20 °C or below for longer studies
- **Residue count:** 344 amino acids
- **Protein class:** Activin-binding glycoprotein, TGF-β superfamily antagonist
- **Principal binding partners:** Activin A, myostatin (GDF-8), selected BMPs
- **Isoform relationship:** Precursor isoform to circulating FS-315; distinct from cell-associated FS-288
- **Research areas:** Myostatin inhibition, skeletal-muscle mass regulation, follicular and reproductive biology, fibrosis models

## Description

Follistatin-344 is the recombinant 344-residue isoform of follistatin, an autocrine glycoprotein originally purified from ovarian follicular fluid. What defines follistatin is its tight binding to several TGF-β superfamily members — activin A above all, but also myostatin (GDF-8) and a number of bone morphogenetic proteins. By capturing these ligands before they reach their receptors, it works as a natural extracellular brake on that signalling pathway.

Alternative splicing gives two main isoforms: FS-288, whose heparin-binding C-terminus keeps it mostly attached to cells, and FS-315, the circulating form. FS-344 is the precursor that becomes FS-315 once its signal peptide is removed, and it is the isoform recombinant laboratories most often express. As myostatin restrains skeletal muscle growth, follistatin has remained a steady focus of muscle-biology and gene-transfer research since the 1990s.

## Frequently asked questions

### What is Follistatin-344, and how does it differ from FS-288 and FS-315?

FS-344 is follistatin's 344-residue precursor isoform. Removing its signal peptide produces FS-315, the form found in circulation, whereas FS-288 is a shorter, heparin-binding variant that remains bound to cells. All share the activin-binding core but differ in where they are found and how they behave.

### Why does it cost more than most peptides?

Because it is a recombinant glycoprotein of 344 residues and about 37.8 kDa, not a short synthetic peptide. It has to be expressed in a biological system and then purified and analysed in several steps — far more work than solid-phase peptide synthesis.

### Is it independently tested, and can I get a COA?

Yes. An independent lab analyses every lot for purity and identity, and the certificate matches the lot number on your vial. Request it either before you order or once the vial has arrived.

### How should it be stored and reconstituted?

Store the sealed lyophilised vial at −20 °C, away from light and humidity. Reconstitute gently in sterile water without shaking, split the solution into single-use aliquots and avoid repeated freezing and thawing — recombinant proteins of this size degrade faster than small peptides.

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All products offered on this website are intended solely for in-vitro laboratory research and development by qualified professionals. They are not drugs, foods, cosmetics or dietary supplements, and are not intended to diagnose, treat, cure or prevent any disease. Products must not be introduced into humans or animals in any manner. By purchasing, you confirm that you are a qualified researcher and accept full responsibility for handling and storage in accordance with applicable laws.

Peptide Medix EU · https://peptidemedixeu.com/en/products/follistatin-344/