Protein renaturation by the liquid organic salt ethylammonium nitrate

Summers, Catherine A.; Flowers, Robert A.

doi:10.1110/ps.9.10.2001

Cited by 246 publications

(259 citation statements)

References 44 publications

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“…Ionic liquids have attracted much interest recently as solvents for biomolecules because they are nonaqueous solvents that are able to promote the self-assembly of amphiphiles (29), and they appear to stabilize protein function (30,31), and some can promote, inhibit, or solubilize amyloid fibrils (32)(33)(34). To date, only high concentrations of strong acids such as formic acid and TFA have been reported to depolymerize rodlets to the monomeric form (6).…”

Section: Resultsmentioning

confidence: 99%

Recruitment of Class I Hydrophobins to the Air:Water Interface Initiates a Multi-step Process of Functional Amyloid Formation

Morris

Ren

Macindoe

et al. 2011

Journal of Biological Chemistry

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Class I fungal hydrophobins form amphipathic monolayers composed of amyloid rodlets. This is a remarkable case of functional amyloid formation in that a hydrophobic:hydrophilic interface is required to trigger the self-assembly of the proteins. The mechanism of rodlet formation and the role of the interface in this process have not been well understood. Here, we have studied the effect of a range of additives, including ionic liquids, alcohols, and detergents, on rodlet formation by two class I hydrophobins, EAS and DewA. Although the conformation of the hydrophobins in these different solutions is not altered, we observe that the rate of rodlet formation is slowed as the surface tension of the solution is decreased, regardless of the nature of the additive. These results suggest that interface properties are of critical importance for the recruitment, alignment, and structural rearrangement of the amphipathic hydrophobin monomers. This work gives insight into the forces that drive macromolecular assembly of this unique family of proteins and allows us to propose a three-stage model for the interface-driven formation of rodlets.Class I hydrophobins are a family of small amphipathic proteins that are produced by filamentous fungi in a monomeric form but are able to self-assemble into amphipathic monolayers composed of amyloid-like structures known as rodlets (1-3). The polymerization of the hydrophobins occurs on contact with a hydrophobic:hydrophilic interface, such as an air:water boundary or when hydrophobins are secreted from the spores and come into contact with the air. Members of the hydrophobin family are characterized by the presence of four disulfide bonds. The amphipathic nature of hydrophobins drives them to the surface of solutions, where they reduce the surface tension (1).Some of the functional roles of the class I hydrophobins include acting as a surfactant at the air:water boundary to reduce the surface tension, which is a barrier to aerial growth of hyphae, and also to form a robust protein coat on spores. This coating provides a hydrophobic external surface that resists wetting and thus facilitates spore dispersal in air (4 -6). The class I hydrophobin rodlets share many of the structural characteristics of amyloid fibrils; formation of the insoluble, fibrillar rodlets is accompanied by conformational change to an ordered cross-␤-secondary structure form and the polymerized rodlets, but not the monomeric form of the protein, bind to the dye thioflavin T (ThT) 4 (2, 7, 8). However, in contrast to other amyloid fibrils, which can often be solubilized by treatment with denaturants such as guanidine hydrochloride or solvents such as dimethyl sulfoxide (9), treatment with acids such as formic and TFA has been reported to be the only method capable of depolymerizing hydrophobin rodlets and regenerating the monomeric form of the hydrophobin proteins in solution (10,11). This is similar to the curli and tafi fibrils produced by bacteria, which have been shown to be functional amyloid and which also req...

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Section: Resultsmentioning

confidence: 99%

Recruitment of Class I Hydrophobins to the Air:Water Interface Initiates a Multi-step Process of Functional Amyloid Formation

Morris

Ren

Macindoe

et al. 2011

Journal of Biological Chemistry

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“…To probe this further, we carried out MSP3-heme interaction experiments in a buffer containing ammonium nitrate that did not favor aggregation of MSP3 as was shown by ThT or Congo Red assays (data not shown). A derivative of ammonium nitrate is a well known solute that disrupts aggregation of proteins (65). In the presence of ammonium nitrate, binding of heme was significantly reduced suggesting that heme binding somehow depends on the aggregation of the protein.…”

Section: Discussionmentioning

confidence: 99%

Plasmodium falciparum Merozoite Surface Protein 3

Imam

Singh

Kaushik

et al. 2014

Journal of Biological Chemistry

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Background: Plasmodium falciparum merozoite surface protein 3 (MSP3) oligomerizes and binds heme. Results: MSP3 forms amyloid-like structures that bind ϳ35 heme molecules, and these filamentous structures are also present on the surface of merozoites. Conclusion: Amyloid formation by MSP3 is related to heme binding. Significance: The presence of MSP3 fibrils on merozoite surface and significant heme binding suggest its functional role during erythrocytic stages of P. falciparum.

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“…We have found that the activity of protease is highly maintained not only in water-immiscible aprotic ionic liquids but also in water-miscible aprotic ionic liquids as well [22,23]. On the other hand, it has been reported that protic ionic liquids keep the stability of proteins in an aqueous solution at high temperatures [24,25], and amyloid fibrils of proteins are dissolved in protic ionic liquids and are refolded by dilution with an aqueous solution [32]. Moreover, aprotic ionic liquids can refold the denatured protein [33].…”

Section: Introductionmentioning

confidence: 93%

“…On the other hand, C, protein aggregation is prevented, and any cloudy appearance is absent [25]. The hydrophobic core of lysozyme unfolded by heat interacts with the cation of ionic liquids, and cation adsorption results in acquisition of a net positive charge preventing aggregation via electrostatic repulsion [24]. Figure 4 shows the relationship between temperature and the remaining activity of lysozyme in aqueous solutions containing water-miscible ionic liquids after the heat treatment for 30 min.…”

Section: Thermal Inactivation Of Lysozymementioning

confidence: 99%