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Molecular Chaperones and Protein Folding

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The native conformation of a protein is formed by interactions between the side chains of its constituent amino acids. When the amino acids cannot form these interactions, the protein cannot fold by itself and needs chaperones. Notably, chaperones do not relay any additional information required for the folding of polypeptides; the native conformation of a protein is determined solely by its amino acid sequence. Chaperones catalyze protein folding without being a part of the folded protein.
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Related Experiment Video

Updated: Jan 10, 2026

Identification of Functional Protein Regions Through Chimeric Protein Construction

Identification of Functional Protein Regions Through Chimeric Protein Construction

Published on: January 8, 2019

Ancestral Chaperonins Provide the First Structural Glimpse into Early Multimeric Protein Evolution.

Rita Severino^1,2, Jorge Cuéllar³, Jorge Gutiérrez-Seijo³

¹Centro de Astrobiología (CAB), INTA-CSIC, Madrid, Spain.

Molecular Biology and Evolution

|November 28, 2025

Summary

This summary is machine-generated.

Researchers resurrected ancient chaperonins, revealing their protein-folding functions and unique structures. This study reconstructs the evolution of these essential molecular machines and their early complexity.

Keywords:

ASR ATPase activity Protein resurrection chaperonins cryoEM evolutionary intermediates multimeric complexity oligomeric states

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Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

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Published on: July 14, 2015

Area of Science:

Molecular Biology
Evolutionary Biology
Structural Biology

Background:

Chaperonins are vital protein-folding machines, categorized into three main groups: Group I (bacterial GroEL), Group II (archaeal thermosome and eukaryotic CCT), and Group III (bacterial thermosome-like).
Understanding the evolutionary origins of these complex multimeric proteins is crucial for comprehending early cellular life.

Purpose of the Study:

To reconstruct and experimentally characterize the last common ancestors of the three major chaperonin groups using ancestral sequence reconstruction (ASR) and protein resurrection.
To elucidate the structural and functional properties of these ancient chaperonins and their evolutionary implications.

Main Methods:

Ancestral sequence reconstruction (ASR) to infer ancestral protein sequences.
Protein resurrection to express and purify inferred ancestral chaperonins (ACI, ACII, ACIII).
Biochemical assays (ATPase activity, client protein protection assays) and structural analyses (electron microscopy, Cryo-EM).

Main Results:

Resurrected ancestral chaperonins (ACI, ACII, ACIII) displayed ATPase activity (except ACII) and protected client proteins from heat denaturation.
Structural analysis revealed ACI formed single 7-mer rings, while ACII exhibited a mix of single and double 8-mer rings, indicating intermediate oligomeric states.
ACII demonstrated a novel cochaperonin-independent closure mechanism, distinct from extant Group I and II chaperonins.

Conclusions:

This study provides the first experimental structural reconstruction of ancient multimeric proteins, offering insights into early protein evolution.
Novel intermediate oligomeric states and unique functional mechanisms in ancestral chaperonins were uncovered, shedding light on the emergence of molecular complexity.
The findings establish an empirical framework for studying the evolution of chaperonins and the origins of multimeric protein machinery in primordial cells.