Osmolytes are a class of small organic molecules that shift the protein folding equilibrium. For this reason, they are accumulated by organisms under environmental stress and find applications in biotechnology where proteins need to be stabilized or dissolved. However, despite years of research, debate continues over the exact mechanisms underpinning the stabilizing and denaturing effect of osmolytes. Here, we simulated the mechanical denaturation of lysozyme in different solvent conditions to study the molecular mechanism by which two biologically relevant osmolytes, denaturing (urea) and stabilizing (betaine), affect the folding equilibrium. We found that urea interacts favorably with all types of residues via both hydrogen bonds and dispersion forces, and therefore accumulates in a diffuse solvation shell around the protein. This not only provides an enthalpic stabilization of the unfolded state, but also weakens the hydrophobic effect, as hydrophobic forces promote the association of urea with nonpolar residues, facilitating the unfolding. In contrast, we observed that betaine is excluded from the protein backbone and nonpolar side chains, but is accumulated near the basic residues, yielding a nonuniform distribution of betaine molecules at the protein surface. Spatially resolved solvent–protein interaction energies further suggested that betaine behaves in a ligand- rather than solvent-like manner and its exclusion from the protein surface arises mostly from the scarcity of favorable binding sites. Finally, we found that, in the presence of betaine, the reduced ability of water molecules to solvate the protein results in an additional enthalpic contribution to the betaine-induced stabilization.
Skip Nav Destination
Article navigation
October 2016
-
Cover Image
Cover Image
A representation of a mitochondrion. In this issue, Kowaltowski et al. review aspects of mitochondrial biology that have an impact on aging in model organisms and selected mammalian cells and tissues. See pp. 3421–3449 for further details.
Research Article|
October 11 2016
Molecular basis of the osmolyte effect on protein stability: a lesson from the mechanical unfolding of lysozyme
Beata Adamczak;
Beata Adamczak
*
Department of Physical Chemistry, Gdansk University of Technology, Narutowicza 11/12, Gdan´sk 80-233, Poland
Search for other works by this author on:
Miłosz Wieczór;
Miłosz Wieczór
*
Department of Physical Chemistry, Gdansk University of Technology, Narutowicza 11/12, Gdan´sk 80-233, Poland
Search for other works by this author on:
Mateusz Kogut;
Mateusz Kogut
Department of Physical Chemistry, Gdansk University of Technology, Narutowicza 11/12, Gdan´sk 80-233, Poland
Search for other works by this author on:
Janusz Stangret;
Janusz Stangret
Department of Physical Chemistry, Gdansk University of Technology, Narutowicza 11/12, Gdan´sk 80-233, Poland
Search for other works by this author on:
Jacek Czub
Jacek Czub
Department of Physical Chemistry, Gdansk University of Technology, Narutowicza 11/12, Gdan´sk 80-233, Poland
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
June 16 2016
Revision Received:
July 25 2016
Accepted:
August 16 2016
Accepted Manuscript online:
August 17 2016
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 2016 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society
2016
Biochem J (2016) 473 (20): 3705–3724.
Article history
Received:
June 16 2016
Revision Received:
July 25 2016
Accepted:
August 16 2016
Accepted Manuscript online:
August 17 2016
Citation
Beata Adamczak, Miłosz Wieczór, Mateusz Kogut, Janusz Stangret, Jacek Czub; Molecular basis of the osmolyte effect on protein stability: a lesson from the mechanical unfolding of lysozyme. Biochem J 15 October 2016; 473 (20): 3705–3724. doi: https://doi.org/10.1042/BCJ20160604
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.