Toward a mechanism for GroEL.GroES chaperone activity: an ATPase-gated and -pulsed folding and annealing cage.
Free GroEL binds denatured proteins very tightly: it retards the folding of barnase 400-fold and catalyzes unfolding fluctuations in native barnase and its folding intermediate. GroEL undergoes an allosteric transition from its tight-binding T-state to a weaker binding R-state on the cooperative binding of nucleotides (ATP/ADP) and GroES. The preformed GroEL.GroES.nucleotide complex retards the folding of barnase by only a factor of 4, and the folding rate is much higher than the ATPase activity that releases GroES from the complex. Binding of GroES and nucleotides to a preformed GroEL.denatured-barnase complex forms an intermediately fast-folding complex. We propose the following mechanism for the molecular chaperone. Denatured proteins bind to the resting GroEL.GroES.nucleotide complex. Fast-folding proteins are ejected as native structures before ATP hydrolysis. Slow-folding proteins enter chaperoning cycles of annealing and folding after the initial ATP hydrolysis. This step causes transient release of GroES and formation of the GroEL.denatured-protein complexes with higher annealing potential. The intermediately fast-folding complex is formed on subsequent rebinding of GroES. The ATPase activity of GroEL.GroES is thus the gatekeeper that selects for initial entry of slow-folding proteins to the chaperone action and then pumps successive transitions from the faster-folding R-states to the tighter-binding/stronger annealing T-states. The molecular chaperone acts as a combination of folding cage and an annealing machine.
Corrales
F J
FJ
Medical Research Council Unit for Protein Function and Design, University of Cambridge, United Kingdom.
Fersht
A R
AR
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins; D018835:Chaperonin 10 / Q000378:metabolism*; D018834:Chaperonin 60 / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry* / Q000378:metabolism*
D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D011994:Recombinant Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D012260:Ribonucleases; C019760:Bacillus amyloliquefaciens ribonuclease