PDIA1(Protein disulfide-isomerase) is also named as ERBA2L,PDI,P4HB,PO4DB. It is a multifunctional protein that catalyzes the formation,breakage and rearrangement of disulfide bonds. In some cell types,it seems to be secreted or associated with the plasma membrane,where it undergoes constant shedding and replacement from intracellular sources.It can exsit as homodimer and monomers and homotetramers may also occur.