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The Rigid Core and Flexible Surface of Amyloid Fibrils Probed by Magic-Angle-Spinning NMR Spectroscopy of Aromatic Residues |
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| Authors: | Lea Marie Becker Mélanie Berbon Alicia Vallet Axelle Grelard Estelle Morvan Benjamin Bardiaux Roman Lichtenecker Matthias Ernst Antoine Loquet Paul Schanda |
| Institution: | 1. Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria;2. Univ. Bordeaux, CNRS, Bordeaux INP, CBMN, UMR, 5248, IECB Pessac, France;3. Institut de Biologie Structurale, 41, avenue des martyrs, Grenoble, France;4. Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US01, Pessac, France;5. Bacterial Transmembrane Systems Unit, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France;6. Institute of Organic Chemistry, University of Vienna, Währinger Str. 38, 1090 Vienna, Austria;7. Physical Chemistry, ETH Zürich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland |
| Abstract: | Aromatic side chains are important reporters of the plasticity of proteins, and often form important contacts in protein–protein interactions. We studied aromatic residues in the two structurally homologous cross-β amyloid fibrils HET-s, and HELLF by employing a specific isotope-labeling approach and magic-angle-spinning NMR. The dynamic behavior of the aromatic residues Phe and Tyr indicates that the hydrophobic amyloid core is rigid, without any sign of “breathing motions” over hundreds of milliseconds at least. Aromatic residues exposed at the fibril surface have a rigid ring axis but undergo ring flips on a variety of time scales from nanoseconds to microseconds. Our approach provides direct insight into hydrophobic-core motions, enabling a better evaluation of the conformational heterogeneity generated from an NMR structural ensemble of such amyloid cross-β architecture. |
| Keywords: | Aromatic Side Chains Isotopic Labeling Protein Dynamics Ring Flips Spin Relaxation |