Regulates protein folding in the endoplasmic reticulum lumen. Probably acts as a J-protein for the Hsp70-type chaperone KAR2 by stimulating its ATP-dependent reaction cycle and initiating folding reactions. Also involved in the endoplasmic reticulum-associated degradation (ERAD) process. Cooperates with KAR2 and another J-protein JEM1 to facilitate the export of ERAD substrates to the cytoplasm by maintaining them in a translocation-competent state and preventing their aggregation in the endoplasmic reticulum lumen. Present with 8260 molecules/cell in log phase SD medium.