Protein folding in the cytosol: chaperonin-dependent and -independent mechanisms.
Recent findings suggest that a combination of chaperonin-assisted and unassisted mechanisms operate in protein folding in the cytosol. While nascent chain-binding chaperones, such as Hsp70, could have a general role in maintaining the folding competence of translating polypeptide chains, the contribution of the cylindrical chaperonin complexes to overall folding is limited to a subset of aggregation-sensitive polypeptides. The majority of bacterial proteins are relatively small and they are synthesized rapidly and folded independently of the chaperonin GroEL in a posttranslational manner. Eukaryotes have a proportionally larger number of multi-domain proteins than bacteria. The individual domains of these proteins can be folded cotranslationally and sequentially. The use of this mechanism explains how large proteins fold independently of a chaperonin and could have been crucial in the evolution of a wide array of modular polypeptides in eukaryotes.
Netzer
W J
WJ
Cornell Graduate School of Medical Sciences, New York, NY 10021, USA.
Hartl
F U
FU
D001426:Bacterial Proteins / Q000378:metabolism; D005075:Biological Evolution; D018834:Chaperonin 60 / Q000378:metabolism; D018833:Chaperonins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D008954:Models, Biological; D014176:Protein Biosynthesis; D017510:Protein Folding
D001426:Bacterial Proteins; D018834:Chaperonin 60; D018840:HSP70 Heat-Shock Proteins; D018833:Chaperonins