Recombinant Human GASP-2/WFIKKN Protein

Growth and differentiation factor-associated serum protein-2 (GASP-2) cDNA encodes a 548 amino acid protein that contains a 19 amino acid signal sequence and is comprised of many conserved domains: WAP, follistatin/Kazal, immunoglobulin, two tandem Kunitz, and netrin (1). Based on the order of these conserved domains, GASP-2 is also known as WFIKKN (1). Another related protein which contains the same domain structure is called WFIKKNRP (WFIKKN-related protein), or GASP-1 (2, 3). WAP, follistatin, Kunitz and netrin domains are all implicated in protease inhibition, and the GASP proteins may be multivalent protease inhibitors (1, 4). Tests at R&D systems have measured the ability of GASP-2 to inhibit trypsin cleavage of the fluorogenic peptide substrate Mca-RPKPVE-Nval-WRK(Dnp)-NH₂ (R&D Systems Catalog # ES002). The IC₅₀ value was approximately 10 nM, as measured in a reaction mixture containing 1.0 nM trypsin, 10 µM ES002, 50 mM Tris, 10 mM CaCl2, 0.15 M NaCl, pH 7.5.

GASP-1 and -2 show distinct expression patterns both in the developing fetus and the adult. In the developing fetus, GASP-2 is abundant in the lung, skeletal muscle and liver while GASP-1 expression is highest in the brain, skeletal muscle, thymus and kidney (3). In the adult, GASP-2 is expressed primarily in the pancreas, liver, and thymus while GASP-1 is in the ovary, testis, and brain (3). Further characterization shows that GASP-1 inhibits myostatin (GDF-8) and the highly related protein, GDF-11, but not Activin or TGF-beta in vitro (2). Although, this kind of activity has not been reported for GASP-2, tests at R&D Systems have determined that GASP-2 shows similar inhibitory activity towards myostatin as GASP-1. By amino acid sequence, human GASP-2 is 55% identical to human GASP-1.