The members of the molecular chaperone families are widely distributed from prokaryotes to eukaryotic cells. The molecular chaperones function in vivo to recognize and stabilize unfolded or partially folded polypeptides, and protect polypeptides from inappropriate intra- or interchain interaction. In some circumstances, the chaperones interact with native proteins and promote rearrangement of oligomeric complexes. Stemming from their ability to recognize and modulate the state of folding of polypeptides within cells, the molecular chaperones serve many functions including mediating mitochondrial protein translocation, regulating signal pathway and being involved in microtubule nucleation.