Related Experiment Video
Updated: Jun 12, 2026
04:37
High-Pressure NMR Experiments for Detecting Protein Low-Lying Conformational States
Published on: June 29, 2021
Denatured states of low-complexity polypeptide sequences differ dramatically from those of foldable sequences
Franco O Tzul1, Bruce E Bowler
1Department of Chemistry and Biochemistry, Biochemistry Program and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA.
Summary
Protein primary sequences guide early folding. Researchers studied yeast iso-1-cytochrome c variants with polyalanine inserts, finding that foldable sequences deviate from random coil behavior, indicating a fold-dependent mechanism in protein folding.
Area of Science:
- Protein folding dynamics
- Biophysics
- Molecular biology
Background:
- Understanding how a protein's primary sequence dictates its early folding steps to achieve the correct native structure is a significant challenge in protein science.
- Early conformational preferences encoded in the amino acid sequence are crucial for efficient and accurate protein folding.
- The precise mechanisms by which sequences guide folding pathways remain poorly understood.
Purpose of the Study:
- To investigate how protein primary sequence influences early folding events.
- To characterize the behavior of polyalanine inserts in the denatured state of yeast iso-1-cytochrome c.
- To compare the folding behavior of designed sequences with known protein sequences.
Main Methods:
- Preparation of yeast iso-1-cytochrome c variants with varying lengths of polyalanine inserts (6-30 residues) near the N-terminus.
- Thermodynamic and kinetic studies of His-heme loop formation in the denatured state using guanidine-hydrochloride (GdnHCl) concentrations of 3 M and 6 M.
- Analysis of scaling exponents for equilibrium loop formation and loop breakage rates.
Main Results:
- Polyalanine inserts in the denatured state approximate a random coil with excluded volume, exhibiting specific scaling exponents (nu(3) = 2.26 +/- 0.13 in 3 M GdnHCl, 1.97 +/- 0.04 in 6 M GdnHCl).
- Loop breakage rates for polyalanine inserts initially decrease with size and then become independent, consistent with random coil behavior.
- Foldable protein sequences, unlike polyalanine, deviate significantly from random coil behavior during denatured state loop formation.
- The extent of deviation from random coil behavior is dependent on the specific protein fold.
Conclusions:
- The primary sequence encodes conformational preferences that guide early folding events.
- Polyalanine serves as a useful model for random coil behavior in protein folding studies.
- Foldable sequences exhibit non-random coil characteristics in the denatured state, highlighting the sequence-structure relationship in protein folding.
- The observed deviations are fold-dependent, suggesting that specific protein architectures influence the folding process from the denatured state.
Related Concept Videos
01:25Protein 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 Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...
01:22Protein Folding
Overview
01:22Protein Folding
Overview
03:00Molecular Chaperones and Protein Folding
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.
The...
The...
03:00Molecular Chaperones and Protein Folding
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.
The...
The...
01:28Protein Denaturation
The function of proteins depends on their native three-dimensional structure, which is dictated by the amino acid sequence of the specific protein. Folding of the polypeptide chain takes place under specific conditions that energetically favor the folded conformation. In contrast, protein denaturation occurs spontaneously under unfavorable conditions that disrupt the integrity of the folded conformation. Thus, the chemical and physical environment of a protein, such as significant changes in pH...