Follistatin-344 (FST344) is a single-chain glycoprotein, one of the two principal biologically active isoforms produced from the follistatin (FST) gene. AminoOptimization Group supplies it as a lyophilised research powder in a 1 mg presentation, tested to 99% purity by HPLC, with a Certificate of Analysis available for the lot supplied. This material is offered strictly for laboratory research use. It is not a drug, and it is not for human or veterinary use.
What is Follistatin-344?
Follistatin was first characterised as a secreted protein that binds and neutralises activin, and the FST gene transcript is processed into two principal isoforms that differ in their C-terminal sequence. FST315, the 315-residue form, carries an acidic C-terminal extension and is the isoform that predominates in circulating plasma. FST344 lacks that extension. Published work attributes this difference to a substantially higher affinity for cell-surface heparan sulfate proteoglycans, which anchors FST344 locally at the tissue level rather than allowing it to circulate freely — a distinction researchers use to separate systemic from tissue-localised activin neutralisation in study design.
Structurally, follistatin is built from an N-terminal domain (ND) followed by three tandem follistatin domains (FSD1, FSD2, FSD3), each stabilised by a conserved pattern of disulfide bonds that produces a compact, cysteine-rich fold. Together these domains form a bipartite binding surface that wraps around ligands of the TGF-β superfamily — activin A is the most extensively studied, alongside myostatin (GDF-8), GDF-11, and select bone morphogenetic proteins — occluding the epitopes those ligands use to assemble with type I and type II activin receptors.
Follistatin-344 is also distinct from follistatin-like 3 (FSTL3, sometimes called FLRG), a separately encoded protein that shares the follistatin domain architecture but binds activin and myostatin with different relative affinities. The two are not interchangeable in the published literature, and study designs that reference “follistatin” without specifying isoform or paralogue are a recurring source of confusion in the field.
Specifications
- Compound: Follistatin-344 (FST344)
- CAS number: Not assigned (recombinant protein)
- Molecular formula: Not applicable (glycoprotein)
- Molecular weight: ~38 kDa (344-residue chain)
- Purity: 99% HPLC
- Product class: Recombinant protein
- Presentation: Lyophilised powder, sealed vial
- Available sizes: 1MG
- Physical form: White to off-white powder
- Classification: Research protein — not for human or veterinary use
Research context
Follistatin research centres on its role as an endogenous antagonist of TGF-β superfamily signalling, with the largest body of published work directed at activin A and myostatin engagement of the ActRIIB receptor complex. In model systems, follistatin binding is examined for how it interferes with ligand-receptor assembly and the downstream phosphorylation of SMAD2/3, the transcription factors through which activin and myostatin signalling is propagated.
Because FST344’s higher affinity for cell-surface heparan sulfate proteoglycans keeps it comparatively localised rather than freely circulating, it appears in study designs that compare local versus systemic neutralisation of activin and myostatin signalling. It is also examined in cell culture and animal-model literature addressing skeletal muscle and gonadal tissue, the two systems in which activin/myostatin signalling is most extensively characterised.
None of this literature establishes safety or efficacy for use in humans. It is provided as research context only.
Reconstitution
Lyophilised protein requires reconstitution with a suitable sterile diluent before use in solution. Bacteriostatic water is the diluent most commonly specified for multi-use laboratory preparations; sterile water is typical for single-use work.
Direct the diluent stream against the inner wall of the vial rather than onto the powder itself, and allow the material to dissolve without agitation. As with other recombinant proteins of this size, Follistatin-344 is susceptible to shear stress and surface denaturation — do not shake the vial. Swirl gently if needed, and allow additional time for full dissolution compared with smaller peptides.
Working concentration is a function of how much diluent is added to a given vial mass. Our peptide reconstitution calculator computes the resulting concentration for any combination of vial size and diluent volume.
Storage and stability
Before reconstitution: store the sealed vial in a freezer at -20 °C, protected from light. Lyophilised protein is comparatively stable in this state. Brief excursions to ambient temperature during shipping are normal and are not expected to compromise a properly lyophilised product.
After reconstitution: refrigerate at 2–8 °C and protect from light. Reconstituted protein in solution is materially less stable than the dry powder, and larger proteins such as follistatin are generally more prone to aggregation than short-chain peptides. Avoid repeated freeze-thaw cycles, which are a well-documented cause of aggregation and loss of measurable activity — aliquot instead if repeated sampling is required.
Inspect solutions before use. Cloudiness, visible particulate, or discolouration indicate the material should not be relied upon for quantitative work.
Certificate of Analysis
Every lot is tested by high-performance liquid chromatography, and the purity figure shown above refers to analytical results for the specific lot supplied — not to a generic specification. A Certificate of Analysis is available on request, and we will provide lot-specific documentation before purchase if your protocol requires it.
Purity by HPLC describes the proportion of the target protein relative to detectable related substances. It is a statement about the material as manufactured and tested. It is expressly not a representation that the material is suitable for any use in humans or animals.
Handling and safety
Handle in accordance with good laboratory practice. Use appropriate personal protective equipment, work in a suitable containment environment, and dispose of material and consumables according to your institution’s requirements and applicable local regulation. Anyone with access to this material should understand that it is not for human or veterinary use.
Frequently asked questions
What is the difference between Follistatin-344 and Follistatin-315?
FST315 carries an acidic C-terminal extension and is the form that predominates in circulating plasma. FST344 lacks that extension and, according to published work, binds cell-surface heparan sulfate proteoglycans with substantially higher affinity, which keeps it more locally tissue-associated. Researchers select between the two isoforms based on whether their study design calls for systemic or localised activin neutralisation.
Is Follistatin-344 approved in Canada?
No. This compound has not been evaluated or authorised by Health Canada, the FDA, or any comparable regulatory authority. It carries no DIN or NPN, its safety and efficacy for human use have not been assessed, and it is supplied for laboratory research only.
How much diluent should be used to reconstitute Follistatin-344?
That depends on the working concentration your protocol requires. Use the reconstitution calculator to work out the resulting concentration for your vial size and diluent volume.
How long is reconstituted Follistatin-344 stable?
Stability in solution is shorter than in lyophilised form and depends on diluent, temperature, and handling. Refrigerate at 2–8 °C, protect from light, avoid freeze-thaw cycling, and validate stability for your own storage conditions if your work depends on it.
Do you provide a Certificate of Analysis?
Yes — lot-specific, available on request, including before purchase.
Research use only
This product is supplied solely for laboratory and scientific research. It is not a drug, food, cosmetic, or medical device, and it must not be administered to humans or animals. Nothing on this page is medical advice or a therapeutic claim. Full terms are set out in our Research Use Only Disclaimer.
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