Activin A is a member of the TGFβ superfamily of growth factors used in stem cell differentiation and maintenance. Activin A Plus, an engineered optimized form of Activin A, incorporates an N-terminal truncation to remove a disulfide-linked extension. The resulting protein can be manufactured at extremely consistent high yield with no observed changes in bioactivity compared to the wild-type. This form is particularly suitable for large scale stem cell culture processes.
Activin A is involved in regulation of embryogenesis, development of the reproductive system, wound healing and regulation of immune responses in vivo. The activity of Activin A is regulated by the high-affinity inhibitor, follistatin1, and inhibins. Activins are disulfide-linked homo- and heterodimers of four inhibin β chains. The best characterized are Activin A and Activin B, homodimers of inhibin βA and inhibin βB respectively. Activins, like all other members in the TGF-β superfamily, are synthesized as larger precursors consisting of an N-terminal signal peptide, a pro-domain of 250–350 residues and a highly conserved mature domain. The pro-domain, which is cleaved off in the mature protein, has important roles in the biosynthesis, stabilization, transportation and signalling of the growth factors2.