Required for protein translocation and folding in the endoplasmic reticulum (ER). Functions as a nucleotide exchange factor for the ER lumenal chaperone HSPA5. Interacts with HSPA5. Highly expressed in tissues which produce large amounts of secreted proteins such as kidney, liver and placenta. Also expressed in colon, heart, lung, ovary, pancreas, peripheral leukocyte, prostate, spleen and thymus. Expressed at low levels throughout the brain. Expressed in fetal kidney, fetal lung, fetal liver and at low levels in fetal brain. N-glycosylated. Ubiquitinated by the CRL2(FEM1A) and CRL2(FEM1C) complexes, which recognize the -Lys-Xaa-Xaa-Arg C-degron at the C-terminus, leading to its degradation. The disease is caused by variants affecting the gene represented in this entry. Belongs to the SIL1 family.