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 has an N-terminal ER-signal sequence, two thioredoxin (TRX) domains with non-classical Ser-Lys-Gln-Ser and Ser-Lys-Lys-Cys motifs, respectively, two TRX-like domains, and a C-terminal ER-retention sequence. The protein lacks oxidoreductase activity in vitro and probably functions as a chaperone. This gene's expression appears to be limited to the testis. [provided by RefSeq, Dec 2016].