>90%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.
<0.10 EU per 1 μg of the protein by the LAL method.
Measured by its ability to induce hemoglobin expression in K562 human chronic myelogenous leukemia cells. Schwall, R.H. et al. (1991) Method Enzymol. 198:340. The ED50 for this effect is 0.6‑3.6 ng/mL.
Chinese Hamster Ovary cell line, CHO-derived Ser21-Ser426
Recombinant Human Latent Activin A (Catalog # 9129-LA) induces hemoglobin expression in K562 human chronic myelogenous leukemia cells. The ED50 is 0.6-3.6 ng/mL.
Background: Activin A
Activin and Inhibin are members of the TGF-beta superfamily of cytokines and are involved in a wide range of biological processes including tissue morphogenesis and repair, fibrosis, inflammation, neural development, hematopoiesis, reproductive system function, and carcinogenesis (1-7). The amino terminal propeptides of Activin and Inhibin are proteolytically cleaved and facilitate formation of disulfide-linked dimers of the bioactive proteins (8, 9). The propeptide of Activin remains associated with the bioactive protein in a latent complex that retains the ability to bind its receptors (10). Activins are nonglycosylated homodimers or heterodimers of various beta subunits ( beta A, beta B, beta C, and beta E in mammals), while Inhibins are heterodimers of a unique alpha subunit and one of the beta subunits. Activin A is a widely expressed homodimer of two beta A chains. The beta A subunit can also heterodimerize with a beta B or beta C subunit to form Activin AB and Activin AC, respectively (11). The 14 kDa mature human beta A chain shares 100% amino acid sequence identity with bovine, feline, mouse, porcine, and rat beta A. Activin A exerts its biological activities by binding to the type 2 serine/threonine kinase Activin RIIA which then noncovalently associates with the type 1 serine/threonine kinase Activin RIB/ALK-4 (7, 12). Signaling through this receptor complex leads to Smad activation and regulation of activin-responsive gene transcription (7, 12). The bioactivity of Activin A is regulated by a variety of mechanisms (12). BAMBI, Betaglycan, and Cripto are cell-associated molecules that function as decoy receptors or limit the ability of Activin A to induce receptor complex assembly (13-15). The intracellular formation of Activin A can be prevented by the incorporation of the beta A subunit into Activin AC or Inhibin A (3, 11). And the bioavailability of Activin A is restricted by its incorporation into inactive complexes with alpha 2-Macroglobulin, Follistatin, and FLRG (16, 17).
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