Inhibition of Amyloid Formation by Ionic Liquids: Ionic Liquids Affecting Intermediate Oligomers

Kalhor, Hamid Reza; Kamizi, Mostafa; Âkbari, Jafar; Heydari, Akbar

doi:10.1021/bm900428q

Cited by 77 publications

(93 citation statements)

References 56 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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“…Tetramethylguinidium acetate decreased amyloid formation by nearly 50% in vitro, and led to thinner fibrils. 411 The conversion of Aβ monomers to Aβ amyloid fibrils was conducted in PIL−water solutions using the PILs consisting of the cations ethylammonium, diethylammonium, or triethylammonium paired with the methanesulfonate anion. 425 Increasing the substitution on the ammonium cation decreased the fibril formation, and it was suggested that this was due to differences in the hydrogenbonded network.…”

Section: Protein Stabilizationmentioning

confidence: 99%

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

2015

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“…20 One recent article on hen egg white lysozyme fibril formation in ionic liquids found no correlation with anion size/type, but the concentration used in the study was much lower than what is used typically to demonstrate Hofmeister effects. 21 …”

Section: 15mentioning

confidence: 99%

The Hofmeister effect on amyloid formation using yeast prion protein

et al. 2009

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A variety of proteins are capable of converting from their soluble forms into highly ordered fibrous cross-b aggregates (amyloids). This conversion is associated with certain pathological conditions in mammals, such as Alzheimer disease, and provides a basis for the infectious or hereditary protein isoforms (prions), causing neurodegenerative disorders in mammals and controlling heritable phenotypes in yeast. The N-proximal region of the yeast prion protein Sup35 (Sup35NM) is frequently used as a model system for amyloid conversion studies in vitro. Traditionally, amyloids are recognized by their ability to bind Congo Red dye specific to b-sheet rich structures. However, methods for quantifying amyloid fibril formation thus far were based on measurements linking Congo Red absorbance to concentration of insulin fibrils and may not be directly applicable to other amyloid-forming proteins. Here, we present a corrected formula for measuring amyloid formation of Sup35NM by Congo Red assay. By utilizing this corrected procedure, we explore the effect of different sodium salts on the lag time and maximum rate of amyloid formation by Sup35NM. We find that increased kosmotropicity promotes amyloid polymerization in accordance with the Hofmeister series. In contrast, chaotropes inhibit polymerization, with the strength of inhibition correlating with the B-viscosity coefficient of the Jones-Dole equation, an increasingly accepted measure for the quantification of the Hofmeister series.

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Inhibition of Amyloid Formation by Ionic Liquids: Ionic Liquids Affecting Intermediate Oligomers

Cited by 77 publications

References 56 publications

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

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

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

The Hofmeister effect on amyloid formation using yeast prion protein

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