title: In vivo observation of polypeptide flux through the bacterial chaperonin system.
abstract: The quantitative contribution of chaperonin GroEL to protein folding in E. coli was analyzed. A diverse set of newly synthesized polypeptides, predominantly between 10-55 kDa, interacts with GroEL, accounting for 10%-15% of all cytoplasmic protein under normal growth conditions, and for 30% or more upon exposure to heat stress. Most proteins leave GroEL rapidly within 10-30 s. We distinguish three classes of substrate proteins: (I) proteins with a chaperonin-independent folding pathway; (II) proteins, more than 50% of total, with an intermediate chaperonin dependence for which normally only a small fraction transits GroEL; and (III) a set of highly chaperonin-dependent proteins, many of which dissociate slowly from GroEL and probably require sequestration of aggregation-sensitive intermediates within the GroEL cavity for successful folding.
authors.affiliation: Howard Hughes Medical Institute and Cellular Biochemistry and Biophysics Program, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Ewalt
authors.forename: J P
authors.initials: JP
authors.lastname: Hendrick
authors.forename: W A
authors.initials: WA
authors.lastname: Houry
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry*; D018834:Chaperonin 60 / Q000378:metabolism*; D018833:Chaperonins / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008961:Models, Structural; D010957:Plasmids; D014176:Protein Biosynthesis; D017510:Protein Folding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D013884:Thiosulfate Sulfurtransferase / Q000096:biosynthesis / Q000737:chemistry; D001618:beta-Lactamases / Q000096:biosynthesis / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D018834:Chaperonin 60; D011994:Recombinant Proteins; D015500:Chloramphenicol O-Acetyltransferase; D013884:Thiosulfate Sulfurtransferase; D001618:beta-Lactamases; D018833:Chaperonins