May function as a chaperone that inhibits aggregation of misfolded proteins . Negatively regulates the unfolded protein response (UPR) through binding to UPR sensors such as ERN1, which in turn inactivates ERN1 signaling . May also regulate the UPR via the EIF2AK3 UPR sensor . Plays a role in platelet aggregation and activation by agonists such as convulxin, collagen and thrombin .
Subcellular locations: Endoplasmic reticulum lumen, Cell membrane, Melanosome
Identified by mass spectrometry in melanosome fractions from stage I to stage IV .
Expressed in platelets (at protein level).