title: Principles of chaperone-assisted protein folding: differences between in vitro and in vivo mechanisms.
abstract: Molecular chaperones in the eukaryotic cytosol were shown to interact differently with chemically denatured proteins and their newly translated counterparts. During refolding from denaturant, actin partitioned freely between 70-kilodalton heat shock protein, the bulk cytosol, and the chaperonin TCP1-ring complex. In contrast, during cell-free translation, the chaperones were recruited to the elongating polypeptide and protected it from exposure to the bulk cytosol during folding. Posttranslational cycling between chaperone-bound and free states was observed with subunits of oligomeric proteins and with aberrant polypeptides; this cycling allowed the subunits to assemble and the aberrant polypeptides to be degraded. Thus, folding, oligomerization, and degradation are linked hierarchically to ensure the correct fate of newly synthesized polypeptides.
authors.affiliation: Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.
authors.forename: J
authors.initials: J
authors.lastname: Frydman
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002457:Cell Extracts; D018834:Chaperonin 60 / Q000737:chemistry / Q000378:metabolism; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins / Q000737:chemistry / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism; D008156:Luciferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012156:Reticulocytes; D012270:Ribosomes / Q000378:metabolism
chemical_list: D000199:Actins; D002457:Cell Extracts; D018834:Chaperonin 60; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D010455:Peptides; D000255:Adenosine Triphosphate; D008156:Luciferases; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins