DnaJ is a heat shock induced protein from the bacterium Escherichia coli which is under control of thr htpr regulatory protein. DnaJ interacts with the chaperone Hsp70-like DnaK protein to disassemble a protein complex found at a phage lambda's origin of replication (ORI). Also, DnaJ with the joint effort of GrpE stimulates the ATPase activity of DnaK. DnaJ, DnaK, and GrpE are all involved in a variety of biological processes: protein folding and transport, cell survival at high temperatures, negative autoregulation of the heat shock response, and the replication of bacteriophage lambda and other plasmids.
DnaJ is 376 amino acid residues long. However, the N-terminal amino acid residues 2-108 retain much of the entire protein's biological function and capabilities. Within this region is the J domain, comprised of residues 2-72. It consists of four alpha helices: 1=Blue, 2=Green, 3=Pink, and 4=Gold. Helices 2 and 3 are in an antiparallel fashion, and in the center of this polypeptide fragment is a conserved hydrophobic core.