Format

Send to

Choose Destination
See comment in PubMed Commons below
J Am Chem Soc. 2010 Aug 4;132(30):10445-52. doi: 10.1021/ja103166y.

Macromolecular crowding remodels the energy landscape of a protein by favoring a more compact unfolded state.

Author information

1
Department of Biochemistry & Molecular Biology, University of Massachusetts, 710 North Pleasant Street, Amherst, Massachusetts 01003, USA.

Abstract

The interior of cells is highly crowded with macromolecules, which impacts all physiological processes. To explore how macromolecular crowding may influence cellular protein folding, we interrogated the folding landscape of a model beta-rich protein, cellular retinoic acid-binding protein I (CRABP I), in the presence of an inert crowding agent (Ficoll 70). Urea titrations revealed a crowding-induced change in the water-accessible polar amide surface of its denatured state, based on an observed ca. 15% decrease in the change in unfolding free energy with respect to urea concentration (the m-value), and the effect of crowding on the equilibrium stability of CRABP I was less than our experimental error (i.e., < or = 1.2 kcal/mol). Consequently, we directly probed the effect of crowding on the denatured state of CRABP I by measuring side-chain accessibility using iodide quenching of tryptophan fluorescence and chemical modification of cysteines. We observed that the urea-denatured state is more compact under crowded conditions, and the observed extent of reduction of the m-value by crowding agent is fully consistent with the extent of reduction of the accessibility of the Trp and Cys probes, suggesting a random and nonspecific compaction of the unfolded state. The thermodynamic consequences of crowding-induced compaction are discussed. In addition, over a wide range of Ficoll concentration, crowding significantly retarded the unfolding kinetics of CRABP I without influencing the urea dependence of the unfolding rate, arguing for no appreciable change in the nature of the transition state. Our results demonstrate how macromolecular crowding may influence protein folding by effects on both the unfolded state ensemble and unfolding kinetics.

PMID:
20662522
PMCID:
PMC2921862
DOI:
10.1021/ja103166y
[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for American Chemical Society Icon for PubMed Central
    Loading ...
    Support Center