The product contains the polyhedrin protein co-crystalized with Human Activin B. Activin B is a member of the TGF-β superfamily, which are disulfide-linked dimeric proteins that were originally purified from gonadal fluids and had as primary role to stimulate the release of pituitary follicle stimulating hormones (FSH). Activin B has shown to have a wide range of biological activities including: mesoderm induction, neural cell differentiation, bone remodeling, hematopoiesis, reproductive physiology, and hormone secretion from the hypothalamic, pituitary and gonadal glands. Activins exert their biological activities through binding to the heterodimeric complex composed of two membrane spanning serine-threonine kinases designated as type I and type II. Two forms of activin receptor type I (Act RI-A and Act RI-B) and two forms of activin receptor type II (Act RII-A and Act RII-B) have been identified. Activin B signals through the ActRII receptor (Activin Receptor type II).