Specifically binds unfolded proteins and may recruit protein disulfide isomerase PDIA3 to unfolded substrates (PubMed:16940051, PubMed:23192347). Binds protein substrates via a hydrophobic pocket in the C-terminal domain (PubMed:16940051, PubMed:23192347). May play a role in the unfolded stress response (PubMed:23192347). Interacts with PDIA3. Induced by ER stress. Belongs to the protein disulfide isomerase family. Does not contain a CXXC active site motif indicating that it is a catalytically redox-inactive member of the protein disulfide isomerase family.