The constitutive and stress inducible forms of hsp 70 exhibit functional similarities and interact with one another in an ATP-dependent fashion

Heat shock protein (hsp) 73 and hsp 72 represent inducible and constitutive forms of heat shock proteins, respectively. Immunoprecipitation and gel electrophoretic analyses showed that hsp 73 and 72 interact with one another. Double-label immunofluorescence and microinjection experiments confirmed this interaction in vivo. Furthermore, the interaction between these two heat shock proteins required the presence of ATP. The implications of this ATP-dependent interaction is discussed in regard to the structure and function of these proteins in normal and stressed cells.