TGFBRAP1 plays a role in the TGF-beta/activin signaling pathway. It associates with inactive heteromeric TGF-beta and activin receptor complexes, mainly through the type II receptor, and is released upon activation of signaling. It may recruit SMAD4 to the vicinity of the receptor complex and facilitate its interaction with receptor-regulated Smads, such as SMAD2. Recombinant human TGFBRAP1 protein, fused to His-tag at N-terminus, was expressed in E.coli.