Counteraction of Urea by Trimethylamine N-Oxide Is Due to Direct Interaction

Meersman, Filip; Bowron, Daniel T.; Soper, A. K.; Koch, Michel H. J.

doi:10.1016/j.bpj.2009.08.017

Cited by 127 publications

(202 citation statements)

References 45 publications

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“…Isotopic substitution neutron-scattering measurements of ternary-component urea-TMAO mixtures in water previously suggested that TMAO interacts directly with urea through preferential hydrogen bonding (59). However, recent studies show that the interaction affinity between the two osmolytes is too weak to be relevant even at high osmolyte concentrations (60,61).…”

Section: Resultsmentioning

confidence: 99%

Counteracting chemical chaperone effects on the single-molecule α-synuclein structural landscape

Ferreon

Moosa

Gambin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Protein structure and function depend on a close interplay between intrinsic folding energy landscapes and the chemistry of the protein environment. Osmolytes are small-molecule compounds that can act as chemical chaperones by altering the environment in a cellular context. Despite their importance, detailed studies on the role of these chemical chaperones in modulating structure and dimensions of intrinsically disordered proteins have been limited. Here, we used single-molecule Förster resonance energy transfer to test the counteraction hypothesis of counterbalancing effects between the protecting osmolyte trimethylamine-N-oxide (TMAO) and denaturing osmolyte urea for the case of α-synuclein, a Parkinson's disease-linked protein whose monomer exhibits significant disorder. The single-molecule experiments, which avoid complications from protein aggregation, do not exhibit clear solvent-induced cooperative protein transitions for these osmolytes, unlike results from previous studies on globular proteins. Our data demonstrate the ability of TMAO and urea to shift α-synuclein structures towards either more compact or expanded average dimensions. Strikingly, the experiments directly reveal that a 2∶1 ½urea∶½TMAO ratio has a net neutral effect on the protein's dimensions, a result that holds regardless of the absolute osmolyte concentrations. Our findings shed light on a surprisingly simple aspect of the interplay between urea and TMAO on α-synuclein in the context of intrinsically disordered proteins, with potential implications for the biological roles of such chemical chaperones. The results also highlight the strengths of single-molecule experiments in directly probing the chemical physics of protein structure and disorder in more chemically complex environments.Parkinson's disease | protein folding | urea-TMAO counteraction | smFRET P roteins are dynamic entities that are in constant interaction with their environment. Several components of the protein environment can affect the folding landscape (1) and function, including solvents (2), osmolytes (3), crowding agents (4), and small-molecule and macromolecular ligands (5-7). Osmolytes are naturally occurring low-molecular weight compounds that are utilized by biological systems as chemical chaperones that counteract deleterious effects of extreme physical conditions such as high osmotic and hydrostatic pressures (8, 9), dehydration (10), and high or low temperatures (11, 12). Urea, a major metabolic byproduct, is known to be used as a balancing osmolyte by several marine vertebrates (8), air-breathing teleosts (13) and some amphibians (14, 15) to deal with osmotic stress. In mammalian kidneys, urea plays an important role in balancing the medullary osmotic gradient (16). However, even at physiologically relevant concentrations, urea shows a strong denaturing effect on proteins (8,17). This apparent paradox is solved by the activity of several protecting osmolytes (e.g., methylamines and polyhydric alcohols) found in these urea-rich biological systems (8,18,19).T...

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Section: Resultsmentioning

confidence: 99%

Counteracting chemical chaperone effects on the single-molecule α-synuclein structural landscape

Ferreon

Moosa

Gambin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Pertinently, it has been found that elasmobranches even during the embryo development accumulate both urea and TMAO together (Barton et al, 1999). Furthermore the mechanism of urea-methylamine counteraction has been understood in terms of thermodynamic, atomic and molecular levels (Burg and Peters, 1997;Burg et al, 1999;Kumar and Kishore, 2013;Lin and Timasheff, 1994;Meersman et al, 2009;Singh et al, 2007). In recent years, there has been no such article that addresses and discusses major developments on this front.…”

Section: Introductionmentioning

confidence: 99%

A current perspective on the compensatory effects of urea and methylamine on protein stability and function

Rahman

Warepam

Singh

et al. 2015

Progress in Biophysics and Molecular Biology

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“…1, Inset) adopts a skewed tetrahedral structure with a charged oxygen capable of accepting hydrogen bonds (H bonds) and three hydrophobic (methyl) groups. This amphiphilic structural arrangement makes TMAO a rather special cosolvent, because it can form H bonds with water, self-associate in a manner similar to surfactants, and show preferential interactions with or exclusion (4)(5)(6)(7)(8)(9)(10)(11)(12) from certain protein functional groups (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Indeed, these molecular properties of TMAO have been used, either individually or in combination, to rationalize its biological activities.…”

mentioning

confidence: 99%

Microscopic insights into the protein-stabilizing effect of trimethylamine N-oxide (TMAO)

Pazos

Gai

2014

Proc. Natl. Acad. Sci. U.S.A.

227

237

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Although it is widely known that trimethylamine N-oxide (TMAO), an osmolyte used by nature, stabilizes the folded state of proteins, the underlying mechanism of action is not entirely understood. To gain further insight into this important biological phenomenon, we use the C≡N stretching vibration of an unnatural amino acid, p-cyano-phenylalanine, to directly probe how TMAO affects the hydration and conformational dynamics of a model peptide and a small protein. By assessing how the lineshape and spectral diffusion properties of this vibration change with cosolvent conditions, we are able to show that TMAO achieves its protein-stabilizing ability through the combination of (at least) two mechanisms: (i) It decreases the hydrogen bonding ability of water and hence the stability of the unfolded state, and (ii) it acts as a molecular crowder, as suggested by a recent computational study, that can increase the stability of the folded state via the excluded volume effect.N ature employs a variety of small organic molecules to cope with osmotic stress. Trimethylamine N-oxide (TMAO) is one such naturally occurring osmolyte that protects intracellular components against disruptive stress conditions (1). In particular, previous studies have shown that TMAO is able to enhance protein stability and to counteract the denaturing effect of urea (2, 3). TMAO (Fig. 1, Inset) adopts a skewed tetrahedral structure with a charged oxygen capable of accepting hydrogen bonds (H bonds) and three hydrophobic (methyl) groups. This amphiphilic structural arrangement makes TMAO a rather special cosolvent, because it can form H bonds with water, self-associate in a manner similar to surfactants, and show preferential interactions with or exclusion (4-12) from certain protein functional groups (13-23). Indeed, these molecular properties of TMAO have been used, either individually or in combination, to rationalize its biological activities. For example, a prevailing view about TMAO is that its osmotic and protective role is caused by the molecule's tendency to be preferentially depleted from protein surfaces, as suggested by physicochemical measurements (24-28). This thermodynamic picture, as described by Bolen and coworkers (29), implies that the protein is preferentially hydrated. Although this notion is consistent with TMAO's being a protecting osmolyte, to the best of our knowledge no experimental studies have been carried out to directly examine the effect of TMAO on protein hydration dynamics, an aspect that is also important to protein function. Herein, we use twodimensional infrared (2D IR) spectroscopy and a site-specific IR probe to explore this critical issue and gain insight toward achieving a microscopic understanding of the molecular mechanism of the protecting action of TMAO.2D IR spectroscopy is capable of assessing the frequencyfrequency correlation function (FFCF) of a given IR probe, which reports on the underlying dynamics of events that lead to fluctuations of its vibrational frequency (30). For an IR probe that is able ...

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Counteraction of Urea by Trimethylamine N-Oxide Is Due to Direct Interaction

Cited by 127 publications

References 45 publications

Counteracting chemical chaperone effects on the single-molecule α-synuclein structural landscape

Counteracting chemical chaperone effects on the single-molecule α-synuclein structural landscape

A current perspective on the compensatory effects of urea and methylamine on protein stability and function

Microscopic insights into the protein-stabilizing effect of trimethylamine N-oxide (TMAO)

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