From minichaperone to groel 3: Properties of an active single-ring mutant of groel

Jean Chatellier, Fergal Hill, Nicholas W. Foster, Pierre Goloubinoff, Alan R. Fersht

Research output: Contribution to journalArticlepeer-review

Abstract

The next step in our reductional analysis of GroEL was to study the activity of an isolated single seven-membered ring of the 14-mer. A known single-ring mutant, GroELSR1, contains four point mutations that prevent the formation of double-rings. That heptameric complex is functionally inactive because it is unable to release GroES. We found that the mutation E191G, which is responsible for the temperature sensitive (ts) Escherichia coli allele groEL44 and is located in the hinge region between the intermediate and apical domains of GroEL, appears to function by weakening the binding of GroES, without destabilizing the overall structure of GroEL44 mutant. We introduced, therefore, the mutation E191G into GroELSR1 in order to generate a single-ring mutant that may have weaker binding of GroES and hence be active. The new single-ring mutant, GroELSR44, was indeed effective in refolding both heat and dithiothreitol-denatured mitochondrial malate dehydrogenase with great efficiency. Further, unlike all smaller constructs of GroEL, the expression of GroELSR44 in E. coli that contained no endogenous GroEL restored biological viability, but not as efficiently as does wild-type GroEL. We envisage the notional evolution of the structure and properties of GroEL. The minichaperone core acts as a primitive chaperone by providing a binding surface for denatured states that prevents their self-aggregation. The assembly of seven minichaperones into a ring then enhances substrate binding by introducing avidity. The acquisition of binding sites for ATP then allows the modulation of substrate binding by introducing the allosteric mechanism that causes cycling between strong and weak binding sites. This is accompanied by the acquisition by the heptamer of the binding of GroES, which ftmctions as a lid to the central cavity and competes for peptide binding sites. Finally, dimerization of the heptamer enhancesits biological activity.

Original languageEnglish
Pages (from-to)897-910
Number of pages14
JournalJournal of Molecular Biology
Volume304
Issue number5
DOIs
StatePublished - 15 Dec 2000
Externally publishedYes

Funding

FundersFunder number
European Commission

    Keywords

    • Cpn60
    • Heat Shock
    • Hsp60
    • Minichaperone
    • Protein folding

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