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Solid-state NMR characterization of tau in paired helical filaments and bound to microtubules as well as of toxic and non-toxic oligomers of a-synuclein and tau.

Subject Area Structural Biology
Term from 2009 to 2016
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 145328088
 
Final Report Year 2016

Final Report Abstract

In this project we have investigated different pathological states of the proteins α-synuclein and tau, which play a role in Parkinson’s and Alzheimer’s disease, respectively. Using solid-state NMR (ssNMR) spectroscopy we could determine the core regions of paired helical filaments (PHFs) formed by a three-repeat variant of tau and also of α-synuclein (mouse) fibrils. In tau PHFs, three β-strands located all in microtubule-binding repeat three could be identified. For mouse α-synuclein fibrils, we found that the rigid core structure comprises six β-strands located between residues G41 and V95. In both cases we could determine the supramolecular arrangement to be a parallel, in-register β-sheet structure. This latter aspect also involved the application of tailored methods to study supramolecular arrangements. Additionally, we then applied these methods that we had originally developed for amyloid fibrils to the study of a functional supramolecular assembly, the type three secretion system (T3SS) needle. This molecular machine is used by pathogenic bacteria to inject virulence factors into host cells. Using our new methods we could determine an atomic model of the T3SS needle whose structure was unknown before (see also the press release of the Max Planck Society: http://www.mpibpc.mpg.de/590161/news_publication_5801544). Subsequently we have presented a refined structure of the type III secretion needle on the basis of solid-state NMR data and a 7.7-Å cryo-EM density map. This collaborative work has also led to the development of a new hybrid structural determination approach which integrates ssNMR and cryo-EM data. We have also investigated a variety of oligomeric species of α-synuclein. On the one hand we studied on-pathway toxic pore-forming oligomers obtained by colddissociation of amyloid fibrils. On the other hand we studied off-pathway oligomers induced by the presence of small aggregation-inhibiting compounds. Lastly, we have installed a dynamic nuclear polarization setup at the Max Planck Institute for Biophysical Chemistry, Göttingen that allows to enhance the ssNMR sensitivity dramatically (14.1 T wide-bore spectrometer; first test measurements yielded an enhancement factor ~30 for type iii secretion needles). This setup will be available for future work on tau-microtubule interactions.

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