Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

35-POS Board 35 Teaming up Molecular Dynamics Simulations with Mass-Spectrometry and ssNMR to Reveal the Dynamic Architecture of the Amyloid Precursor Protein’s Transmembrane Domain Alexander Götz 1 , Hannes Heinel 2 , Philipp Högel 3 , Alexander Vogel 2 , Dieter Langosch 3 , Daniel Huster 2 , Christina Scharnagl 1 . 1 Technical University of Munich, Garching, Germany, 3 Technical University of Munich, Freising, Germany. 2 University of Leipzig, Leipzig, Germany, Alzheimer’s disease (AD) is characterized by accumulation of toxic β-amyloid (Aβ) in the brain and neuronal death. Aβ peptides of different lengths are produced by stepwise proteolytic cleavage within the transmembrane domain (TMD) of the amyloid precursor protein (APP) by γ- secretase. Aβ toxicity is related to fragment length, which correlates with cleavage at ε48 or ε49. Mutations located in the C-terminal domain of APP (TM-C) shift production towards the longer, aggregation-prone Aβ42, associated with early-onset familial AD (FAD). No FAD mutations are known for the N-terminal domain (TM-N) as well as the central GGVV hinge region. A highly anisotropic TMD fluctuation pattern defines a hierarchically organized substrate dynamic. To further investigate the dynamic architecture of the APP TMD, a joint approach of molecular dynamics simulations, mass-spectrometry and solid-state nuclear magnetic resonance is used, comparing wild-type (WT) APP with designed G38L, G38P and the I45T FAD mutant. The TMD’s intrinsic dynamics is studied in POPC and POPE/POPG bilayers, while the environment of substrate bound in γ-secretase’s aqueous active site is mimicked by a TFE/H 2 O mixture. No mutant enhances helix unwinding at the scissile bonds locally. Rather, G38 mutants affect fluctuations in TM-N, while increased fluctuations upstream the ε-sites in I45T are consistent with our results for other FADs. Different solvents induce mainly differences of the extent of TMD fluctuations. Lipid composition does not impact the TMD’s internal dynamics, but enforces different overall rotational dynamics. Since TM-C dynamics is associated with disease’s onset, while TM-N dynamics is not, we propose a model where processing of the substrate utilizes the hierarchy of its TMD flexibility: Binding-induced stiffening of TM-N promotes the functional importance of motions localized in the cleavage domain.

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