Elucidation of the transthyretin denaturation and amyloid fibril formation pathways /
The focus of this dissertation research is to understand the quaternary and tertiary structural changes which facilitate acid mediated transthyretin (TTR) amyloid fibril formation and to evaluate the difference between wild type and FAP disease-associated variants of TTR. At physiological concentra...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739669421&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The focus of this dissertation research is to understand the quaternary and tertiary structural changes which facilitate acid mediated transthyretin (TTR) amyloid fibril formation and to evaluate the difference between wild type and FAP disease-associated variants of TTR. At physiological concentrations, tetrameric TTR remains associated from pH 7 to 5.5 and is incapable of amyloid formation. At pHs below 5, TTR exists in an ensemble of intermediates with different quaternary structures. The distribution of these association states of TTR is strongly influenced by the exact pH, temperature, and TTR concentration. A ladder of species having a molecular weight difference of about 14 KDa suggests that monomeric TTR is the building block of the array of quaternary structural species identified. Amyloid fibril formation occurs over a narrow pH range (5-3.5), implying that there are subtle differences between the TTR tertiary and quaternary structures below this pH range when compared to the species at the amyloidogenic pHs. Spectroscopic studies were carried out to characterize the structural features of the amyloidogenic intermediates. These studies suggest that the intermediates at the amyloidogenic pHs have non-native, yet defined secondary and tertiary structures different from the loosely associated acid molten-globule-like structure of TTR at pH 2. The investigation of the single tryptophan mutants of TTR suggests that Trp-41 is located near the site of the tertiary structural rearrangement that occurs in the formation of the amyloidogenic intermediates, likely involving the C-strand- loop-D-strand region. The denaturation and reconstitution of TTR in GdnHCl was also examined, which is characterized by a marked hysteresis, the transition being separated by 4 M GdnHCl. A rate constant of 4.6 x 10-11 sec- I was obtained for the denaturation of TTR tetramer after the extrapolation of the rate constants to 0 M GdnHCl. The V30M variant, which is the most prevalent FAP variant, dissociates 1000 fold faster than the wild type protein, indicating that these FAP mutants may be kinectically predisposed to amyloid fibril formation. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 142 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 132-139. |