We have recently identified a novel 40-kDa heatshock protein hsp40 as a mammalian homologue of bacterial DnaJ protein. Here we demonstrate the physical interaction between hsp70 (DnaK homologue) and hsp40 in human cells as determined by immunoprecipitation methods. Co-immunoprecipitation of hsp70 with hsp40 was dependent on the presence of ATP or unfolded protein (reduced carboxymethylated alpha-lactalbumin). A mutant type of tumor suppressor gene product, mtp53, was co-immunoprecipitated not only with hsp70 but also with hsp40. These results suggest the existence of a hsp70(DnaK)/hsp40(DnaJ) chaperone system in mammalian cells.
Escherichia coli Proteins Genes, p53