Dokument: Energetics of linear polymerization: a study of amyloid fibril elongation

Titel:	Energetics of linear polymerization: a study of amyloid fibril elongation
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=52050
URN (NBN):	urn:nbn:de:hbz:061-20200122-115435-0
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Vettore, Nicola [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 33,40 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 21.01.2020 / geändert 21.01.2020
Beitragende:	Prof. Dr. Büll, Alexander Kai [Gutachter] Jun.-Prof. Dr. Schröder, Gunnar [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	Supramolecular linear polymers are a class of non-covalent molecular assemblies of relevance in biology and chemistry. Proteins such as actin, tubulin, and flagellin assemble into filaments that are part of this class of polymers. In the cell they have different roles, from the spatial organization to motility. Due to the importance of these functions, thermodynamic characterization of these systems was carried out already in the 1950s. Over the last decades, a different class of protein polymers, amyloid fibrils, have garnered increasing interest due to their relevance in different pathologies, such as Alzheimer’s and Parkison’s disease. Amyloid fibrils are protein filaments characterised by a typical cross-β structure. The kinetics of amyloid formation are objects of numerous studies, but the thermodynamic behaviour is still insufficiently researched. This thesis builds on the current knowledge to lay the foundation for a detailed description of amyloid fibril elongation along its reaction coordinate. In order to be able to describe a reaction it is necessary to evaluate the stability of the species involved. In the amyloid growth reaction this means characterizing the stability of the soluble and amyloid state. In Chapter 2, I compare two models to describe the stability of the amyloid state: the isodesmic and the cooperative one. The isodesmic model, the only one currently in use, proved to be insufficient in describing the complexity of amyloid polymerization. For this purpose, I introduced the cooperative model, through which I was able to characterize the stability of the amyloid state and to describe the salt dependency of the amyloid stability. The different components that contribute to the stability of a species, namely entropy and enthalpy, can be studied by measuring how the stability changes with temperature. In Chapter 3, I analyse the thermal stability of two fibrillar systems, glucagon and PI3K-SH3, as a function of temperature. Two novel models that exploit kinetic out-of-equilibrium behaviour are applied to describe the enthalpic contribution to the stability of the two systems. Alongside the characterization of the amyloid stability, in Chapter 4 a structure of PI3K-SH3 amyloid fibril solved by cryo-EM is presented. The architecture of amyloid fibrils has started to be resolved at atomic level just recently. This contribution to the field allows the rationalization of numerous previous findings related to the mechanism of PI3K-SH3 fibrillation. Ultimately, in Chapter 5, I combine the novel knowledge from the previous chapters to provide the first description of the transition state of the PI3K-SH3 amyloid elongation reaction. By using five mutants to probe different parts of the sequence, the role of the mutated residues in the structural ensemble of the transition state can be inferred. This is possible through the use of the newly-established thermodynamic measurement and the already-established kinetic measurement techniques, which together allowed me to adapt the Φ-value analysis of protein folding to the amyloid elongation reaction. The possibility to investigate the transition state of the amyloid growth reaction paves the way for more detailed characterization of the amyloid fibrillation mechanism.
Lizenz:	Urheberrechtsschutz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Physikalische Biologie
Dokument erstellt am:	22.01.2020
Dateien geändert am:	22.01.2020
Promotionsantrag am:	12.11.2019
Datum der Promotion:	16.12.2019