Recombinant human TPBG (trophoblast glycoprotein), also known as Wnt-activated inhibitory factor 1 (WAIF1), encompassing amino acids 32-355. The C-terminus is fused with the Fc fragment of a human IgG1 followed by an Avi-Tag™. The recombinant protein was enzymatically biotinylated using the Avi-Tag™ and affinity purified.