Three faces of mortalin: a housekeeper, guardian and killer.

Mortalin was first cloned as a mortality factor that existed in the cytoplasmic fractions of normal, but not in immortal, mouse fibroblasts. A decade of efforts have expanded its persona from a house keeper protein involved in mitochondrial import, energy generation and chaperoning of misfolded proteins, to a guardian of stress that has multiple binding partners and to a killer protein that contributes to carcinogenesis on one hand and to old age disorders on the other. Being proved to be an attractive target for cancer therapy, it also warrants attention from the perspectives of management of old age diseases and healthy aging.