1. The Josephin Domain Determines the Morphological and Mechanical Properties of Ataxin-3 Fibrils
- Author
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Annalisa Pastore, Alfonso De Simone, Giuseppe Nicastro, Lesley J. Calder, Laura Masino, Justin E. Molloy, Masino, Laura, Nicastro, Giuseppe, De Simone, Alfonso, Calder, Lesley, Molloy, Justin, Pastore, A, Masino, L., Nicastro, G., De Simone, A., Calder, L., Molloy, J., and Pastore, A.
- Subjects
Biophysics ,Nerve Tissue Proteins ,Fibril ,Protein Structure, Secondary ,medicine ,Humans ,Ataxin-3 ,Protein secondary structure ,Mechanical Phenomena ,Persistence length ,Atomic force microscopy ,Chemistry ,Protein ,Temperature ,Nuclear Proteins ,Disease family ,medicine.disease ,Protein multimerization ,Elasticity ,Biomechanical Phenomena ,Protein Structure, Tertiary ,Repressor Proteins ,Biochemistry ,Ataxin ,Spinocerebellar ataxia ,Protein Multimerization - Abstract
Fibrillar aggregation of the protein ataxin-3 is linked to the inherited neurodegenerative disorder Spinocerebellar ataxia type 3, a member of the polyQ expansion disease family. We previously reported that aggregation and stability of the nonpathological form of ataxin-3, carrying an unexpanded polyQ tract, are modulated by its N-terminal Josephin domain. It was also shown that expanded ataxin-3 aggregates via a two-stage mechanism initially involving Josephin self-association, followed by a polyQ-dependent step. Despite this recent progress, however, the exact mechanism of ataxin-3 fibrilization remains elusive. Here, we have used electron microscopy, atomic force microscopy, and other biophysical techniques to characterize the morphological and mechanical properties of nonexpanded ataxin-3 fibrils. By comparing aggregates of ataxin-3 and of the isolated Josephin domain, we show that the two proteins self-assemble into fibrils with markedly similar features over the temperature range 37-50°C. Estimates of persistence length and Young's modulus of the fibrils reveal a great flexibility. Our data indicate that, under physiological conditions, during early aggregation Josephin retains a nativelike secondary structure but loses its enzymatic activity. The results suggest a key role of Josephin in ataxin-3 fibrillar aggregation. © 2011 by the Biophysical Society.
- Published
- 2011
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