Amyloid fibril formation by human stefin B: Influence of pH and TFE on fibril growth and morphology

Department of Biochemistry, Molecular and Structural Biology, Josef Stefan Institute, Ljubljana, Slovenia.
Amyloid (Impact Factor: 2.01). 10/2007; 14(3):237-47. DOI: 10.1080/13506120701461137
Source: PubMed


As shown before, human stefin B (cystatin B) populates two partly unfolded species, a native-like state at pH 4.8 and a structured molten globule state at pH 3.3 (high ionic strength), from each of which amyloid fibrils grow. Here, we show that the fibrils obtained at pH 3.3 differ from those at pH 4.8 and that those obtained at pH 3.3 (protofibrils) do not transform readily to mature fibrils. In addition we show that amorphous aggregates are also a source of fibrils. The kinetics of amyloid fibril formation at different trifluoroethanol (TFE) concentrations were measured. TFE accelerates fibril growth at predenaturational concentrations of the alcohol. At concentrations higher than 10%, the fibrillar yield decreases proportionately as the population of an all alpha-helical, denatured form of the protein increases. At an optimum TFE concentration, the lag and the growth phases are observed, similarly to some other amyloidogenic proteins. Morphology of the protein species at the beginning and the end of the reactions was observed using atomic force microscopy and transmission electron microscopy. Final fibril morphologies differ depending on solvent conditions.

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    • "2,2,2-Trifluoroethanol (TFE) and its derivatives are commonly used as inhalation anesthetics. It is also used industrially as a solvent for nylon, as a dye and as an ingredient in anti-ulcer agents, anti-arrhythmic drugs etc. Toxicity of TFE has been confirmed on blood, male reproductive system, brain, upper respiratory tract and eyes (Zerovnik et al. 2007). It shifts the equilibrium from native toward denatured state and thus favoring aggregation and subsequent fibril formation. "
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