Chaperonin Mechanisms: Multiple and (Mis)Understood?

Abstract

The chaperonins are ubiquitous and essential nanomachines that assist in protein folding in an ATP-driven manner. They consist of two back-to-back stacked oligomeric rings with cavities in which protein (un)folding can take place in a shielding environment. This review focuses on GroEL from Escherichia coli and the eukaryotic chaperonin-containing t-complex polypeptide 1, which differ considerably in their reaction mechanisms despite sharing a similar overall architecture. Although chaperonins feature in many current biochemistry textbooks after being studied intensively for more than three decades, key aspects of their reaction mechanisms remain under debate and are discussed in this review. In particular, it is unclear whether a universal reaction mechanism operates for all substrates and whether it is passive, i.e., aggregation is prevented but the folding pathway is unaltered, or active. It is also unclear how chaperonin clients are distinguished from nonclients and what are the precise roles of the cofactors with which chaperonins interact. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Temperature Regulates Stability, Ligand Binding (Mg2+ and ATP), and Stoichiometry of GroEL–GroES Complexes

“…Potential roles of bullet- and football-shaped GroEL–GroES complexes (BS- and FB-conformations, respectively) remain somewhat controversial. , Bigman suggests that BS and FB structures may coexist and that their relative activities may be linked to ATP concentrations, which have been shown to be widely variable . A more complete summary of bullet- vs football-shaped GroEL–GroES complexes can be found in a recent review by Horovitz et al…”

Dissecting the Thermodynamics of ATP Binding to GroEL One Nucleotide at a Time

“…2,[5][6][7] The equatorial domain also harbors the ATP binding site for each subunit. 1 While the structure, dynamics, and ATP binding of GroEL has been extensively investigated, [8][9][10][11][12][13][14][15][16][17][18][19][20] we recently reported results using native mass spectrometry (nMS) that reveal new insights about stability and stoichiometry of GroEL-ATP/GroES interactions. 21 Using variable-temperature electrospray ionization (vT-ESI) we found that GroEL-ATP binding was temperature and ATP-concentration dependent, indicating that the thermodynamics of this vital interaction for the GroEL nanomachine might reveal new information as to how the GroEL nanomachine operates.…”

In vitro Evolution of Uracil Glycosylase Towards DnaKJ and GroEL Binding Evolves Different Misfolded States

“…In the case of Hsp70-Hsp40-Hsp110 (DnaK-DnaJ-GrpE in E coli), chaperone-assisted unfolding-refolding occurs via DnaJ-binding motives, enriched with bulky hydrophobic amino acids on the surface of misfolded structures in aggregated polypeptides (Rüdiger et al, 2001) and DnaK-binding motives, generally misfolded structures which, once unfolded, consist of five consecutive hydrophobic residues, flanked by positive charges in un-structured polypeptide segments (Rüdiger et al, 1997). In the case of Hsp60 (GroEL-GroES in E coli), chaperone-assisted unfolding-refolding occurs via cooperative binding of exposed hydrophobic surfaces on aggregation-prone misfolded polypeptides, to a ring of hydrophobic motives displayed by the apical domains of the GroEL heptameric oligomers (Horovitz et al, 2022;Priya et al, 2013b).…”