title: Control of folding and membrane translocation by binding of the chaperone DnaJ to nascent polypeptides.
abstract: Recent evidence supports the view that cellular protein folding may be mediated by molecular chaperones. A fundamental question concerns the stage in its biogenesis at which the folding protein makes first contact with these components. We show here by crosslinking that the chaperone DnaJ binds nascent ribosome-bound polypeptide chains as short as 55 residues. Cotranslational binding of DnaJ to firefly luciferase and chloramphenicol acetyltransferase resulted in an arrest of folding as long as the functional partners of DnaJ in Escherichia coli, DnaK and GrpE, were missing. Protein uptake into microsomes and mitochondria was also interrupted by DnaJ. Both folding and post-translational translocation recommenced upon addition of DnaK and GrpE. We propose that DnaJ protects nascent polypeptide chains against aggregation and, in cooperation with Hsp70, controls their productive folding once a complete polypeptide or a polypeptide domain has been synthesized.
authors.affiliation: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
authors.forename: J P
authors.initials: JP
authors.lastname: Hendrick
authors.forename: T
authors.initials: T
authors.lastname: Langer
authors.forename: T A
authors.initials: TA
authors.lastname: Davis
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
authors.forename: M
authors.initials: M
authors.lastname: Wiedmann
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001667:Binding, Competitive; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D004285:Dogs; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008156:Luciferases / Q000096:biosynthesis; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010179:Pancreas / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D012156:Reticulocytes; D012441:Saccharomyces cerevisiae / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase