Recombinant Human FLRG (FSTL3) (carrier-free)

Pricing & Availability
Other Names
FSTL3, FSRP, Follistatin-Related Protein, Follistatin Like 3, Follistatin-Like 3 (Secreted Glycoprotein), Follistatin-Related Protein 3
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Product Citations
Recombinant human FLRG (FSTL3) antagonizes recombinant human Activin A (Cat. No. 592002, at 30 ng/mL) activity to promote proliferation of MPC-11 cells. The ED50 for this effect is 30 - 120 ng/mL.
  • Human_FLRG_CF_RECOM_1_012220.png
    Recombinant human FLRG (FSTL3) antagonizes recombinant human Activin A (Cat. No. 592002, at 30 ng/mL) activity to promote proliferation of MPC-11 cells. The ED50 for this effect is 30 - 120 ng/mL.
  • Human_FLRG_CF_RECOM_2_012220.png
    Stability Testing for Recombinant Human FLRG (FSTL3). Recombinant human FLRG (FSTL3) was aliquoted in PBS, pH7 at 0.2 mg/mL. One aliquot was frozen and thawed four times (4x Freeze/Thaw) and compared to the control that was kept at 4°C (Control). The samples were tested for their ability to antagonize recombinant human Activin A (Cat. No. 592002, at 30 ng/mL) activity to promote proliferation of MPC-11 cells. The ED50 for this effect is 30 - 120 ng/mL.
Cat # Size Price Save
789602 10 µg ¥17,100
789604 25 µg ¥35,100
789606 100 µg ¥103,500

Human FLRG (Follistatin-related gene) was initially identified from a B-cell chronic lymphocytic leukemia. It is a secreted glycoprotein greatly homologous with follistatin. Activins (A, B, and AB) belonging to the TGF-β superfamily regulate cell proliferation, differentiation, apoptosis, and tumor growth. FLRG and follistatin bind to activin A and antagonize its activity. FLRG and activin A expression are upregulated in hematopoiesis. TGF-β induces the expression of FLRG in bone marrow. FLRG and activin A are expressed in the same cells, with higher expression in myeloid cells than in erythroid and megakaryocytic cells. On the contrary, FLRG and follistatin are expressed in different hematopoietic cells. FLRG and follistatin are associated with tumorigenesis of different tissues. FLRG is highly expressed in infiltrating ductal carcinoma (IDC), and silencing FLRG with small interfering RNA induces tumor growth inhibition. FLRG is overexpressed in invasive breast cancer.

Product Details
Technical data sheet

Product Details

Human FLRG, amino acid (Met27 - Val 263) (Accession: # O95633), with a C-terminal 6His tag, was expressed in CHO cells.
Molecular Mass
The 250 amino acid recombinant protein has a predicted molecular mass of approximately 26.45 kD. The DTT-reduced and non-reduced protein migrates at approximately 35 and 40 kD by SDS-PAGE respectively. The predicted N-terminal amino acid is Met.
>95%, as determined by Coomassie stained SDS-PAGE.
0.22 µm filtered protein solution is in PBS.
Endotoxin Level
Less than 0.1 EU per µg cytokine as determined by the LAL method
10 and 25 µg sizes are bottled at 200 µg/mL. 100 µg and larger sizes are lot-specific and bottled at the concentration indicated on the vial (please contact technical support for concentration, or use our Lookup tool if you have a lot number.)
Storage & Handling
Unopened vial can be stored between 2°C and 8°C for up to 2 weeks at -20°C for up to six months, or at -70°C or colder until the expiration date. For maximum results, quick spin vial prior to opening. The protein can be aliquoted and stored at -20°C or colder. Stock solutions can also be prepared at 50 - 100 µg/mL in appropriate sterile buffer, carrier protein such as 0.2 - 1% BSA or HSA can be added when preparing the stock solution. Aliquots can be stored between 2°C and 8°C for up to one week and stored at -20°C or colder for up to 3 months. Avoid repeated freeze/thaw cycles.
Recombinant human FLRG (FSTL3) antagonizes recombinant human Activin A (Cat. No. 592002, at 30 ng/mL) activity to promote proliferation of MPC-11 cells. The ED50 = 30 - 120 ng/mL.


Application Notes

BioLegend carrier-free recombinant proteins provided in liquid format are shipped on blue ice. Our comparison testing data indicates that when handled and stored as recommended, the liquid format has equal or better stability and shelf-life compared to commercially available lyophilized proteins after reconstitution. Our liquid proteins are verified in-house to maintain activity after shipping on blue ice and are backed by our 100% satisfaction guarantee. If you have any concerns, contact us at

Antigen Details


Highly expressed in myeloid cells, placenta, endometrium, testis, skin, adrenal glands, skeletal muscle, and cardiovascular tissue

Inhibits activin A, activin B, BMP2, and myostatin. Plays a role in bone formation, inhibits osteoclast differentiation.
Activin A, activin B, BMP2, BMP4, and myostatin
Human FLRG antagonizes recombinant human Activin A activity to promote proliferation of MPC-11 cells.
Cell Type
Endothelial cells, Mesenchymal cells, Osteoclasts
Biology Area
Cancer Biomarkers, Cardiovascular Biology, Cell Biology, Cell Proliferation and Viability, Stem Cells
Antigen References
  1. Maguer-Satta V, et al. 2001. Exp Hematol. 29:301.
  2. Hill JJ, et al. 2003. Mol Endocrinol. 17:1144.
  3. Florio P, et al. 2004. Mol Cell Endocrinol. 218:129.
  4. Sidis Y, et al. 2006. Endocrinology. 147:3586.
  5. Razanajaona D, et al. 2007. Cancer Res. 67:7223.
  6. Stamler R, et al. 2008. J Biol Chem. 283:32831.
  7. Couto HL, et al. 2017. Oncotarget. 8:42189
Gene ID
10272 View all products for this Gene ID
View information about FLRG on

Related FAQs

Does specific activity of a recombinant protein vary between lots?

Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.

Have your recombinants been tested for stability?

Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.

How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?
Use formula Specific activity (Units/mg) = 10e6/ ED50 (ng/mL)
How does the activity of your recombinant proteins compare to competitors?

We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!

What is the specific activity or ED50 of my recombinant protein?

The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet. Please note this only applies to recombinants labeled for use in bioassays. ELISA standard recombinant proteins are not recommended for bioassay usage as they are not tested for these applications.

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For research use only. Not for diagnostic use. Not for resale. BioLegend will not be held responsible for patent infringement or other violations that may occur with the use of our products.


*These products may be covered by one or more Limited Use Label Licenses (see the BioLegend Catalog or our website, BioLegend products may not be transferred to third parties, resold, modified for resale, or used to manufacture commercial products, reverse engineer functionally similar materials, or to provide a service to third parties without written approval of BioLegend. By use of these products you accept the terms and conditions of all applicable Limited Use Label Licenses. Unless otherwise indicated, these products are for research use only and are not intended for human or animal diagnostic, therapeutic or commercial use.


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Toll-Free Phone: 1-877-Bio-Legend (246-5343) Phone: (858) 768-5800 Fax: (877) 455-9587

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