Recombinant Human FLRG Protein

Follistatin-related gene protein (FLRG), also known as follistatin-like 3 (FSTL3) is a glycoprotein belonging to the follistatin-module protein family. Human FLRG cDNA encodes a 263 amino acid (aa) residue protein with a putative 26 aa signal peptide, an N-terminal domain, two cysteine-rich follistatin-like domains (FS) and a C-terminal acidic domain. Compared to follistatin, FLRG lacks the third FS domain found in follistatin. In addition, FLRG also lacks the heparin-binding domain found within the first amino-terminal FS domain of follistatin. Mouse and human FLRG share approximately 83% aa sequence homology. Like follistatin, FLRG has been shown to bind and inhibit the activities of TGF-beta family ligands including activin, BMP-2, -6, -7 and GDF-8/myostatin. While both FLRG and follistatin are located in a wide and overlapping range of adult and fetal tissue, their sites of peak expression differ: FLRG most highly in heart, lung, kidney, placenta and testis, while follistatin is highest in ovary and pituitary. The expression of FLRG is upregulated by TGF-beta  and activin signaling through Smad proteins. Although FLRG is a secreted protein in many cell types, it has also been localized to the nuclear compartment in HeLa, 293 and CHO cells (1 - 5).