title: Sequence-resolved free energy profiles of stress-bearing vimentin intermediate filaments.
abstract: Intermediate filaments (IFs) are key to the mechanical strength of metazoan cells. Their basic building blocks are dimeric coiled coils mediating hierarchical assembly of the full-length filaments. Here we use single-molecule force spectroscopy by optical tweezers to assess the folding and stability of coil 2B of the model IF protein vimentin. The coiled coil was unzipped from its N and C termini. When pulling from the C terminus, we observed that the coiled coil was resistant to force owing to the high stability of the C-terminal region. Pulling from the N terminus revealed that the N-terminal half is considerably less stable. The mechanical pulling assay is a unique tool to study and control seed formation and structure propagation of the coiled coil. We then used rigorous theory-based deconvolution for a model-free extraction of the energy landscape and local stability profiles. The data obtained from the two distinct pulling directions complement each other and reveal a tripartite stability of the coiled coil: a labile N-terminal half, followed by a medium stability section and a highly stable region at the far C-terminal end. The different stability regions provide important insight into the mechanics of IF assembly.
authors: Physik Department E22, Technische Universität München, 85748 Garching, Germany;
authors: Beatrice
authors: B
authors: Ramm
authors: Physik Department E22, Technische Universität München, 85748 Garching, Germany;
authors: Johannes
authors: J
authors: Stigler
authors: Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742;
authors: Michael
authors: M
authors: Hinczewski
authors: Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742;
authors: D
authors: D
authors: Thirumalai
authors: Functional Architecture of the Cell, German Cancer Research Center, 69120 Heidelberg, Germany; and.
authors: Harald
authors: H
authors: Herrmann
authors: Physik Department E22, Technische Universität München, 85748 Garching, Germany;
authors: Günther
authors: G
authors: Woehlke
authors: Physik Department E22, Technische Universität München, 85748 Garching, Germany;Nanosystems Initiative Munich, 80799 Munich, Germany mrief@ph.tum.de.
authors: Matthias
authors: M
authors: Rief
mesh_terms: D000595:Amino Acid Sequence; D007382:Intermediate Filaments / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013314:Stress, Mechanical; D013816:Thermodynamics; D014746:Vimentin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014746:Vimentin
keywords: Brownian dynamics simulation; protein folding; trigger sequence