In vivo observation of polypeptide flux through the bacterial chaperonin system.
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.
Ewalt
K L
KL
Howard Hughes Medical Institute and Cellular Biochemistry and Biophysics Program, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.
Hendrick
J P
JP
Houry
W A
WA
Hartl
F U
FU
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
D001426:Bacterial Proteins; D018834:Chaperonin 60; D011994:Recombinant Proteins; D015500:Chloramphenicol O-Acetyltransferase; D013884:Thiosulfate Sulfurtransferase; D001618:beta-Lactamases; D018833:Chaperonins