This gene encodes a member of the disulfide isomerase (PDI) family of endoplasmic reticulum (ER) proteins that catalyze protein folding and thiol-disulfide interchange reactions. The encoded protein has an N-terminal ER-signal sequence, a catalytically active thioredoxin domain, and a C-terminal ER-retention sequence. This gene is expressed in ciliated airway epithelial cells and, in mouse, plays a role in ciliary beat frequency in multiciliated cells. This gene is also over-expressed in breast, ovarian, and prostrate cancers.