Has a pivotal role in cytoprotective cellular mechanisms triggered by oxygen deprivation. May play a role as a molecular chaperone and participate in protein folding. Part of a large chaperone multiprotein complex comprising DNAJB11, HSP90B1, HSPA5, HYOU, PDIA2, PDIA4, PDIA6, PPIB, SDF2L1, UGGT1 and very small amounts of ERP29, but not, or at very low levels, CALR nor CANX. Highly expressed in tissues that contain well-developed endoplasmic reticulum and synthesize large amounts of secretory proteins. Highly expressed in liver and pancreas and lower expression in brain and kidney. Also expressed in macrophages within aortic atherosclerotic plaques, and in breast cancers. By hypoxia and also by 2-deoxyglucose or tunicamycin. The disease may be caused by variants affecting the gene represented in this entry. Belongs to the heat shock protein 70 family.