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Protein Folding

Protein Folding

Protein Folding

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to its biological function. Interactions between its constituent amino acids guide protein folding, and hence the protein structure is primarily dependent on its amino acid sequence.
Protein Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...

Protein Folding

Protein Folding

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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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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The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...

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Related Experiment Video

Updated: Jul 16, 2026

Assays for the Degradation of Misfolded Proteins in Cells

Assays for the Degradation of Misfolded Proteins in Cells

Published on: August 28, 2016

A unified mechanism for protein folding: predetermined pathways with optional errors.

Mallela M G Krishna¹, S Walter Englander

¹Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6059, USA. kmallela@mail.med.upenn.edu

Protein Science : a Publication of the Protein Society

|February 27, 2007

Summary

Protein folding pathways are reconciled by a new hypothesis where optional errors cause apparent multiple pathways. This model explains protein folding behavior more simply than independent unrelated pathways (IUP) models.

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Last Updated: Jul 16, 2026

Assays for the Degradation of Misfolded Proteins in Cells

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Microfluidic Mixers for Studying Protein Folding

Microfluidic Mixers for Studying Protein Folding

Published on: April 10, 2012

Area of Science:

Protein folding dynamics
Biophysics
Structural biology

Background:

Conflicting models exist for protein folding pathways: independent unrelated pathways (IUP) versus a single predetermined pathway.
Kinetic and theoretical studies often support IUP, while structural data suggests a sequential process.

Purpose of the Study:

To resolve the conflict between different protein folding models.
To propose and test the predetermined pathway--optional error (PPOE) hypothesis.

Main Methods:

Compared the PPOE model with the IUP model using kinetic folding data for hen lysozyme.
Analyzed folding behavior based on foldon substructure and sequential stabilization principles.

Main Results:

The PPOE model successfully explains kinetic folding data with fewer parameters.
The PPOE model's fitted scheme aligns with known folding behavior, unlike IUP.
The IUP model's properties are contradicted by experimental results.

Conclusions:

The PPOE hypothesis unifies protein folding explanations by incorporating cooperative foldons, sequential stabilization, and optional errors.
Apparent multiple pathways arise from misfolding errors blocking folding at different stages.
The conflict between models stems from differing focus on microscopic versus macroscopic behavior.