Mitochondrial Hsp70, also known as HSPA9B,Grp75 or mortalin, is a heat-uninducible member of the Hsp70 family of proteins. It is localized in the mitochondrial matrix, where, in concert with Hsp60, it is thought to participate in the refolding of proteins translocated into this organelle. Like its E. coli homolog DnaK, mitochondrial Hsp70 possesses a cation-dependent ATPase activity thought to be central to its function as a chaperone.
Overexpression of this protein leads to extended life span in normal human cells. On the other hand, it serves as a major target for oxidation and is involved in old age pathologies such as Alzheimer's and Parkinson's diseases. Mitochondrial Hsp70 colocalises with p53 in the perinuclear region in many cancer cell lines and is also an attractive target for cancer therapy.