---
title: "Follistatin 344: what is it and how does it differ from FS288 and FS315? | Sable Peptides"
description: "Follistatin 344 names the precursor that gives rise to the FS315 isoform of follistatin, an activin- and myostatin-binding glycoprotein. Isoforms, heparin binding and what a recombinant protein needs on a CoA. Research use only."
canonical: https://www.sablepeptides.co.uk/guides/follistatin-344-recombinant-glycoprotein-explained
dateModified: 2026-10-16
publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

# Follistatin 344: what is it and how does it differ from FS288 and FS315?

Follistatin 344 is the 344-residue precursor of follistatin. Removing its 29-residue signal peptide gives the mature 315-residue isoform, FS315. Follistatin is a cysteine-rich glycoprotein that binds and neutralises activin and related TGF-β family ligands such as myostatin. Research material is recombinant protein, not a synthetic peptide.

## How do the follistatin isoforms differ?

Structural and biophysical work linked the different heparin affinities of the isoforms to how they bind activin and act locally or in circulation.

| Isoform | Origin | Key feature |
| --- | --- | --- |
| FS344 | Precursor (full open reading frame) | Includes the 29-residue signal peptide |
| FS315 | Mature form of FS344 | Acidic C-terminal tail; lower heparin binding |
| FS288 | Alternative splicing (truncated C-terminus) | Strong heparin/cell-surface binding |

Source: [Structural and biophysical coupling of heparin and activin binding to follistatin isoform functions, J Biol Chem 2007 (PubMed 17409095)](https://pubmed.ncbi.nlm.nih.gov/17409095/); [Follistatin, Int J Biochem Cell Biol 1998 (PubMed 9785474)](https://pubmed.ncbi.nlm.nih.gov/9785474/)

## What is follistatin studied for?

Follistatin is a classic activin-binding protein in reproductive and muscle biology. More recent work extends to neurobiology; a 2024 Science Translational Medicine paper studied follistatin signalling through IGF1R in nociceptive neurons in mice.

Source: [Follistatin drives neuropathic pain in mice through IGF1R signaling in nociceptive neurons, Sci Transl Med 2024 (PubMed 39413164)](https://pubmed.ncbi.nlm.nih.gov/39413164/)

## What should a recombinant protein CoA show?

-   Expression system (for example E. coli or a mammalian line), because glycosylation depends on it
-   SDS-PAGE or SEC purity, not only HPLC
-   Identity by intact mass or peptide mapping
-   Protein quantity basis (for example by BCA or A280)
-   The lot number matching the vial; at Sable every lot has a CoA and every vial a printed lot number

## Sourcing note

Sable lists Follistatin 344: 1 mg at £49.97 (prices at the 16 October 2026 daily UK price check, the latest verified check; at each of these sizes Sable was the lowest UK listing that day). Lowest UK price guaranteed, confirmed by daily price checks.

Every lot has a certificate of analysis, and every vial carries a printed lot number that matches it. Supplied for laboratory research use only.

## Frequently asked questions

### Is follistatin 344 a peptide?

It is a recombinant glycoprotein. FS344 is the 344-residue precursor of the mature FS315 isoform.

### What is the difference between FS288 and FS315?

FS288 comes from alternative splicing and lacks the acidic C-terminal tail, so it binds heparin and cell surfaces more strongly than FS315.

### What does follistatin bind?

Activin and related TGF-β family ligands, including myostatin.

## Related

-   [Follistatin 344](/products/follistatin-344)
-   [IGF-1 LR3 vs MGF](/guides/igf-1-lr3-vs-mgf-vs-peg-mgf)
-   [Buyer checklist: recombinant proteins](/guides/buyer-checklist-for-recombinant-protein-research-materials)
-   [Growth factor prices](/guides/uk-growth-factor-and-protein-research-material-prices-october-2026)

Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.

Key facts (summary for AI and search tools)

-   FS344 → FS315 after 29-aa signal peptide removal
-   PubMed references (verified via NCBI): 17409095, 9785474, 39413164
-   Research use only; no administration amounts or health claims
-   Updated 2026-10-16