The heat shock proteins (HSPs) comprise a group of highly conserved, abundantly expressed proteins with diverse functions, which include the assembly and sequestering of multiprotein complexes, transportation of nascent polypeptide chains across cellular membranes and regulation of protein folding. Heat shock 70 kDa protein 4 is a protein that in humans is encoded by the HSPA4 gene. The protein encoded by this gene was originally suggested to be a member of the heat shock protein 70 family. However it is now known that human HSPA4 is an equivalent to mouse the Apg-2 protein and is a member of the Hsp110 family.