Biophysical Society Thematic Meeting | Tutzing 2026

Single-Molecule FRET: The Next 30 Years

Thursday Speaker Abstracts

CONFORMATIONAL DYNAMICS AND CONFORMATIONAL SELECTION OF INTRINSICALLY DISORDERED SNAP25 DURING SNARE COMPLEX ASSEMBLY Tobias Stief 1,2 , Sophia Werner 1,2 , Selcuk Er 2 , Suren Felekyan 3 , Claus A. Seidel 3 , Nils-Alexander Lakomek 1,2,* 1 Institute of Biological Information Processing (IBI-7), Forschungszentrum Jülich, Jülich, Germany 2 Institute of Physical Biology, Faculty of Mathematics and Natural Sciences, University of Düsseldorf, Düsseldorf, Germany 3 Molecular Physical Chemistry, Faculty of Mathematics and Natural Sciences, University of Düsseldorf, Düsseldorf, Germany *correspondence: cseidel@hhu.de, n.lakomek@fz-juelich.de Nuclear Magnetic Resonance (NMR) Spectroscopy and Fluorescence Spectroscopy are highly versatile and complementary techniques to study biomolecules in solution. While NMR spectroscopy provides residue-specific, short-range information in an ensemble manner, fluorescence spectroscopy enables long-range distance measurements on ensembles as well as on single molecules. A particularly wide range of internal dynamics is present in intrinsically disordered proteins (IDPs) and proteins with large intrinsically disordered regions (IDRs), which together comprise about 40% of the human proteome. Here, we use NMR, which will be combined with single-molecule FRET experiments to investigate the conformational dynamics of the SNARE protein SNAP25a, both in its monomeric pre-fusion state and during SNARE complex assembly. SNARE proteins play a crucial role in neuronal exocytosis by mediating the fusion of the synaptic vesicle membrane with the presynaptic plasma membrane. In its pre-fusion state, SNAP25a is intrinsically disordered, except for the N-terminal 35 residues, which are α helical. Intrinsic disorder includes the second half of the N-terminal SNARE motif and the entire C-terminal SNARE motif [1]. According to our (unpublished) NMR data, SNARE complex assembly is a more dynamic process than previously assumed. We hypothesize that the SNAP25a N-terminus acts as a nucleation point during SNARE complex assembly. Pre-existing conformational ensembles may explain how SNARE zippering can occur rapidly in vivo on one side but could also identify possible interference/braking sides for partially zippered SNARE complexes. References [1] Stief T., Gremer L., Pribicevic S., Jahn R., Perez-Lara A., Lakomek N.A., Intrinsic disorder of the SNARE protein SNAP25a in its pre-fusion conformation, J. Mol. Biol. 2023, 435 (10), 168069

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