Structural Features of the GroEL-GroES Nano-Cage Required for Rapid Folding of Encapsulated Protein

Abstract

GroEL and GroES form a chaperonin nano-cage for proteins up to approximately 60 kDa to fold in isolation. Here we explored the structural features of the chaperonin cage critical for rapid folding of encapsulated substrates. Modulating the volume of the GroEL central cavity affected folding speed in accordance with confinement theory. Small proteins (approximately 30 kDa) folded more rapidly as the size of the cage was gradually reduced to a point where restriction in space slowed folding dramatically. For larger proteins (approximately 40-50 kDa), either expanding or reducing cage volume decelerated folding. Additionally, interactions with the C-terminal, mildly hydrophobic Gly-Gly-Met repeat sequences of GroEL protruding into the cavity, and repulsion effects from the negatively charged cavity wall were required for rapid folding of some proteins. We suggest that by combining these features, the chaperonin cage provides a physical environment optimized to catalyze the structural annealing of proteins with kinetically complex folding pathways.

Single-nucleotide variations in the genes encoding the mitochondrial Hsp60/Hsp10 chaperone system and their disease-causing potential

“…Deletion of the entire repeat region in GroEL has indicated that it is dispensable, although deletion had some effect on ATPase activity and the ability to suppress temperature-sensitive mutations (Mclennan et al 1993). Moreover, a recent study showed that replacement of the methionine residues by alanine decelerated folding of a mutant maltose binding protein (Tang et al 2006).…”

Firefly luciferase mutants as sensors of proteome stress

“…The GroEL-GroES machine is a wellorchestrated system where binding of GroES to GroEL leads to allosteric modulation in the GroEL subunits (Xu et al, 1997). This results in expansion of the central cavity, enough to encapsulate a polypeptide of ~ 60 kDa Sakikawa et al, 1999;Tang et al, 2006). Generally, it takes ~ 10 sec for the ATP hydrolysis which drives the folding of intermediates to native tertiary structure inside the GroEL cavity.…”

Human TRiC complex purified from HeLa cells contains all eight CCT subunits and is active in vitro

“…Hsp70 chaperones bind to nascent proteins immediately after exiting the ribosome, while Hsp90 chaperones assist their client proteins at the end of the folding process (Hartl et al 2011). The most complex of the ATP-dependent chaperones, the chaperonins, fold substrates in a cavity within the chaperonin where the substrate is sequestered, in whole or in part, away from the environment of the cell (Thulasiraman et al 1999;Tang et al 2006).…”