Isolation and characterization of a DnaJ-like protein in rats: the C-terminal 10-kDa domain of hsc70 is not essential for stimulating the ATP-hydrolytic activity of hsc70 by a DnaJ-like protein.

A DnaJ-like protein, RDJ1, was isolated from a rat brain cDNA library. The protein is predicted to have 397 amino acid residues and shares 99% identity to that of HDJ2, a human DnaJ-like protein. RDJ1 was also shown to rescue the temperature-sensitive lethality of a strain containing a mutated cytosolic DnaJ in yeast, ydj1-151. Fragments containing the J-domain of RDJ1 either with or without the G/F motif were expressed in Escherichia coli. The purified proteins stimulated the ATPase activity of hsc70 and of the 60-kDa N-terminal fragment of hsc70. These results imply that RDJ1 can interact with the N-terminal 60-kDa fragment of hsc70 to activate ATP hydrolysis by hsc70.