Dry molten globule intermediates and the mechanism of protein unfolding

Robert L. Baldwin, Carl Frieden, George D Rose

Research output: Contribution to journalArticle

Abstract

New experimental results show that either gain or loss of close packing can be observed as a discrete step in protein folding or unfolding reactions. This finding poses a significant challenge to the conventional two-state model of protein folding. Results of interest involve dry molten globule (DMG) intermediates, an expanded form of the protein that lacks appreciable solvent. When an unfolding protein expands to the DMG state, side chains unlock and gain conformational entropy, while liquidlike van der Waals interactions persist. Four unrelated proteins are now known to form DMGs as the first step of unfolding, suggesting that such an intermediate may well be commonplace in both folding and unfolding. Data from the literature show that peptide amide protons are protected in the DMG, indicating that backbone structure is intact despite loss of side-chain close packing. Other complementary evidence shows that secondary structure formation provides a major source of compaction during folding. In our model, the major free-energy barrier separating unfolded from native states usually occurs during the transition between the unfolded state and the DMG. The absence of close packing at this barrier provides an explanation for why φ-values, derived from a Brønsted-Leffler plot, depend primarily on structure at the mutational site and not on specific side-chain interactions. The conventional two-state folding model breaks down when there are DMG intermediates, a realization that has major implications for future experimental work on the mechanism of protein folding.

Original languageEnglish (US)
Pages (from-to)2725-2737
Number of pages13
JournalProteins
Volume78
Issue number13
DOIs
StatePublished - Oct 2010

Fingerprint

Protein Unfolding
Protein Folding
Molten materials
Protein folding
Proteins
Entropy
Amides
Protons
Energy barriers
Peptides
Free energy
Compaction

Keywords

  • Activation volume
  • Close packing
  • Hydrogen bonding
  • Hydrophobic interactions
  • Intermediates
  • Molten globule
  • Protein folding
  • Secondary structure
  • Transition state

ASJC Scopus subject areas

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Cite this

Dry molten globule intermediates and the mechanism of protein unfolding. / Baldwin, Robert L.; Frieden, Carl; Rose, George D.

In: Proteins, Vol. 78, No. 13, 10.2010, p. 2725-2737.

Research output: Contribution to journalArticle

Baldwin, Robert L. ; Frieden, Carl ; Rose, George D. / Dry molten globule intermediates and the mechanism of protein unfolding. In: Proteins. 2010 ; Vol. 78, No. 13. pp. 2725-2737.
@article{12ad8e10ffbf46478b412dad49ba596b,
title = "Dry molten globule intermediates and the mechanism of protein unfolding",
abstract = "New experimental results show that either gain or loss of close packing can be observed as a discrete step in protein folding or unfolding reactions. This finding poses a significant challenge to the conventional two-state model of protein folding. Results of interest involve dry molten globule (DMG) intermediates, an expanded form of the protein that lacks appreciable solvent. When an unfolding protein expands to the DMG state, side chains unlock and gain conformational entropy, while liquidlike van der Waals interactions persist. Four unrelated proteins are now known to form DMGs as the first step of unfolding, suggesting that such an intermediate may well be commonplace in both folding and unfolding. Data from the literature show that peptide amide protons are protected in the DMG, indicating that backbone structure is intact despite loss of side-chain close packing. Other complementary evidence shows that secondary structure formation provides a major source of compaction during folding. In our model, the major free-energy barrier separating unfolded from native states usually occurs during the transition between the unfolded state and the DMG. The absence of close packing at this barrier provides an explanation for why φ-values, derived from a Br{\o}nsted-Leffler plot, depend primarily on structure at the mutational site and not on specific side-chain interactions. The conventional two-state folding model breaks down when there are DMG intermediates, a realization that has major implications for future experimental work on the mechanism of protein folding.",
keywords = "Activation volume, Close packing, Hydrogen bonding, Hydrophobic interactions, Intermediates, Molten globule, Protein folding, Secondary structure, Transition state",
author = "Baldwin, {Robert L.} and Carl Frieden and Rose, {George D}",
year = "2010",
month = "10",
doi = "10.1002/prot.22803",
language = "English (US)",
volume = "78",
pages = "2725--2737",
journal = "Proteins: Structure, Function and Genetics",
issn = "0887-3585",
publisher = "Wiley-Liss Inc.",
number = "13",

}

TY - JOUR

T1 - Dry molten globule intermediates and the mechanism of protein unfolding

AU - Baldwin, Robert L.

AU - Frieden, Carl

AU - Rose, George D

PY - 2010/10

Y1 - 2010/10

N2 - New experimental results show that either gain or loss of close packing can be observed as a discrete step in protein folding or unfolding reactions. This finding poses a significant challenge to the conventional two-state model of protein folding. Results of interest involve dry molten globule (DMG) intermediates, an expanded form of the protein that lacks appreciable solvent. When an unfolding protein expands to the DMG state, side chains unlock and gain conformational entropy, while liquidlike van der Waals interactions persist. Four unrelated proteins are now known to form DMGs as the first step of unfolding, suggesting that such an intermediate may well be commonplace in both folding and unfolding. Data from the literature show that peptide amide protons are protected in the DMG, indicating that backbone structure is intact despite loss of side-chain close packing. Other complementary evidence shows that secondary structure formation provides a major source of compaction during folding. In our model, the major free-energy barrier separating unfolded from native states usually occurs during the transition between the unfolded state and the DMG. The absence of close packing at this barrier provides an explanation for why φ-values, derived from a Brønsted-Leffler plot, depend primarily on structure at the mutational site and not on specific side-chain interactions. The conventional two-state folding model breaks down when there are DMG intermediates, a realization that has major implications for future experimental work on the mechanism of protein folding.

AB - New experimental results show that either gain or loss of close packing can be observed as a discrete step in protein folding or unfolding reactions. This finding poses a significant challenge to the conventional two-state model of protein folding. Results of interest involve dry molten globule (DMG) intermediates, an expanded form of the protein that lacks appreciable solvent. When an unfolding protein expands to the DMG state, side chains unlock and gain conformational entropy, while liquidlike van der Waals interactions persist. Four unrelated proteins are now known to form DMGs as the first step of unfolding, suggesting that such an intermediate may well be commonplace in both folding and unfolding. Data from the literature show that peptide amide protons are protected in the DMG, indicating that backbone structure is intact despite loss of side-chain close packing. Other complementary evidence shows that secondary structure formation provides a major source of compaction during folding. In our model, the major free-energy barrier separating unfolded from native states usually occurs during the transition between the unfolded state and the DMG. The absence of close packing at this barrier provides an explanation for why φ-values, derived from a Brønsted-Leffler plot, depend primarily on structure at the mutational site and not on specific side-chain interactions. The conventional two-state folding model breaks down when there are DMG intermediates, a realization that has major implications for future experimental work on the mechanism of protein folding.

KW - Activation volume

KW - Close packing

KW - Hydrogen bonding

KW - Hydrophobic interactions

KW - Intermediates

KW - Molten globule

KW - Protein folding

KW - Secondary structure

KW - Transition state

UR - http://www.scopus.com/inward/record.url?scp=77957970492&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77957970492&partnerID=8YFLogxK

U2 - 10.1002/prot.22803

DO - 10.1002/prot.22803

M3 - Article

C2 - 20635344

AN - SCOPUS:77957970492

VL - 78

SP - 2725

EP - 2737

JO - Proteins: Structure, Function and Genetics

JF - Proteins: Structure, Function and Genetics

SN - 0887-3585

IS - 13

ER -