Recombinant Human Follistatin-like 4 Protein, CF

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R&D Systems Recombinant Proteins and Enzymes
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Recombinant Human Follistatin-like 4 Protein, CF Summary

Product Specifications

>95%, by SDS-PAGE under reducing conditions and visualized by silver stain
Endotoxin Level
<0.01 EU per 1 μg of the protein by the LAL method.
Measured by its ability to inhibit BMP-6-induced alkaline phosphatase production by MC3T3‑E1 mouse preosteoblast cells. The ED50 for this effect is 2-10 µg/mL in the presence of 0.1 µg/mL of recombinant human BMP-6.
Chinese Hamster Ovary cell line, CHO-derived human Follistatin-like 4/FSTL4 protein
Trp23-Val842, with an N-terminal 7-His tag and Asn
Accession #
N-terminal Sequence
Predicted Molecular Mass
93.6 kDa
100 kDa, reducing conditions

Product Datasheets

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Carrier Free

What does CF mean?

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

What formulation is right for me?

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.


Formulation Lyophilized from a 0.2 μm filtered solution in PBS.
Reconstitution Reconstitute at 300 μg/mL in sterile PBS.
Shipping The product is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage: Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
  • 12 months from date of receipt, -20 to -70 °C as supplied.
  • 1 month, 2 to 8 °C under sterile conditions after reconstitution.
  • 3 months, -20 to -70 °C under sterile conditions after reconstitution.
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Background: Follistatin-like 4/FSTL4

Follistatin-like 4 (FSTL4) is a presumably secreted member of the follistatin domain-containing protein family (1). Follistatin itself is a potent inhibitor of the TGF-beta superfamily member, activin (1, 2), and this activity is reflected in several other proteins of this family that contain varying numbers of the cysteine-rich follistatin domain. Many of these are matrix proteins such as SPARC and testican for which TGF-beta superfamily inhibition status is presumed but unknown (2, 3). R&D Systems recombinant human FSTL4 inhibits the ability of a TGF-beta superfamily member, BMP-6, to induce osteoblast differentiation of a mouse fibroblast cell line. Human FSTL4 cDNA encodes an 842 amino acid (aa) protein containing a 22 aa signal sequence, a follistatin (EGF- and kazal-like) domain, an EF‑hand calcium-binding motif, and two Ig-like cell adhesion molecule-type (IgCAM) domains (1, 4). The second IgCAM domain contains a consensus sequence for FGF/FGF receptor interaction (4). Mature human FSTL4 shares 84%, 82% and 82% aa identity with mouse, rat and bovine FSTL4, respectively. Identity with other follistatin-like family members is mainly within consensus residues of the follistatin domain. Of two reported human FSTL4 isoforms, one is missing the follistatin and EF‑hand domains, while the other contains all recognized domains, but is truncated after aa 600 (4).

  1. Glusman, G. et al. (2004) BMC Evol. Biol. 4:43.
  2. Schneyer, A. et al. (2001) Mol. Cell. Endocrinol. 180:33.
  3. Hohenester, E. et al. (1997) EMBO J. 16:3778.
  4. Swissprot Accession # Q6MZW2.
Entrez Gene IDs
23105 (Human); 320027 (Mouse); 303130 (Rat)
Alternate Names
Follistatin like 4; Follistatin-like 4; Follistatin-like protein 4; follistatin-related protein 4; FSL4; FSTL4; KIAA1061


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