The Effect of Octapeptide on Prion Fibril Conversion
| Autor: | Mei-Yu Huang, 黃玫毓 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 Prion diseases are neurodegenerative disorders carried out in mammalian. These diseases are due to structural conversion of prion protein (PrP) from normal cellular isoform (PrPC) to pathogenic isoform (PrPSc). PrPC is most of α-helical with soluble and protease sensitive. After conversion to PrPSc, protein is β-sheet rich and become insoluble and protease-resistant. According to previous studies, the C-terminal region of prion protein, PrP121-230, is the toxic component to from PrPSc and can be against protease K digestion. Therefore, the flexible N-terminal domain has not been considered to be disease-related. However, recent studies have demonstrated that the onset of familial prion diseases is associated with both point mutation and repetition of octapeptide repeats (OR) insertion in N-terminal OR region, PrP51-91 with 5 OR. OR region of PrPC has Cu2+-binding sites. However, copper binding on PrPC structure and the role in disease have not been fully clarified. Base on these studies, we speculate that the repetition of OR insertion can influence the structure, the fibril formation and protease K-resistant strength of C-terminal region. In this study, we prepared four protein variants (MoPrP ∆octa, MoPrP 1-OR, MoPrP 5-OR (WT), MoPrP 8-OR with and without Cu2+-treatment) for the structure comparison, kinetic study of fibril formation and further characterization of the fibrils. We found that increasing number of the repeats decrease protein α-helical content and the stability of C-terminus, and also affects the kinetics of fibril formation. On the other hand, PrP-8OR proteins and fibrils are more resistant to protease K digestion than other variants. Further, we tested the cell toxicity of the fibrils converted from these protein variants. Cell viability decreased with increasing numbers of OR. This study conclusively indicates that increasing octapeptide repeat affects structure of prion and the conversion to more toxic fibrils. This result provides evidence to elucidate the molecular mechanism of prion disease. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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