title: Interaction of murine BiP/GRP78 with the DnaJ homologue MTJ1.
abstract: The activity of Hsp70 proteins is regulated by accessory proteins, among which the most studied are the members of the DnaJ-like protein family. BiP/GRP78 chaperones the translocation and maturation of secreted and membrane proteins in the endoplasmic reticulum. No DnaJ-like partner has been described so far to regulate the function of mammalian BiP/GRP78. We show here that murine BiP/GRP78 interacts with the lumenal J domain of the murine transmembrane protein MTJ1 (J-MTJ1). J-MTJ1 stimulates the ATPase activity of BiP/GRP78 at stoichiometric concentrations. The C-terminal tail of BiP/GRP78 is not required for the interaction with J-MTJ1, leaving the function of this portion of the molecule still unclear. Physical interactions between J-MTJ1 and BiP/GRP78 are stable and can be abolished by a single histidine --> glutamine substitution in the highly conserved HPD motif shared by all DnaJ-like proteins. The J-MTJ1 fragment, but not the mutant J-MTJ1:H89Q fragment, stimulates the ATPase activity of Escherichia coli DnaK, although at a higher concentration than its genuine partner DnaJ. Full-length DnaJ does not stimulate BiP over the range of concentrations investigated. These results indicate that the J domain of MTJ1 is sufficient for its interaction with BiP/GRP78 and cannot be substituted by E. coli DnaJ.
authors.affiliation: Department of Medicinal Chemistry and Pharmacognosy, University of Illinois, Chicago, Illinois 60607-7173, USA.
authors.forename: M
authors.initials: M
authors.lastname: Chevalier
authors.forename: H
authors.initials: H
authors.lastname: Rhee
authors.forename: E C
authors.initials: EC
authors.lastname: Elguindi
authors.forename: S Y
authors.initials: SY
authors.lastname: Blond
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010957:Plasmids; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C494635:DnaJ protein, E coli; C092319:Dnajc1 protein, mouse; D000091342:Endoplasmic Reticulum Chaperone BiP; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D010455:Peptides; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli