Specifically binds unfolded proteins and may recruit protein disulfide isomerase PDIA3 to unfolded substrates. Binds protein substrates via a hydrophobic pocket in the C-terminal domain. May play a role in the unfolded stress response. Interacts with PDIA3. 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.