Protein disulfide isomerase that catalyzes the formation, isomerization, and reduction or oxidation of disulfide bonds in client proteins and functions as a protein folding chaperone (  ). Core component of the major histocompatibility complex class I (MHC I) peptide loading complex where it functions as an essential folding chaperone for TAPBP. Through TAPBP, assists the dynamic assembly of the MHC I complex with high affinity antigens in the endoplasmic reticulum. Therefore, plays a crucial role in the presentation of antigens to cytotoxic T cells in adaptive immunity (, ).
Subcellular locations: Endoplasmic reticulum, Endoplasmic reticulum lumen, Melanosome
Identified by mass spectrometry in melanosome fractions from stage I to stage IV .
Detected in the flagellum and head region of spermatozoa (at protein level) . Expressed in liver, stomach and colon (at protein level). Expressed in gastric parietal cells and chief cells (at protein level) .