title: Molecular architecture of native fibronectin fibrils.
abstract: Fibronectin fibrils within the extracellular matrix play central roles in physiological and pathological processes, yet many structural details about their hierarchical and molecular assembly remain unknown. Here we combine site-specific protein labelling with single-molecule localization by stepwise photobleaching or direct stochastic optical reconstruction microscopy (dSTORM), and determine the relative positions of various labelled sites within native matrix fibrils. Single end-labelled fibronectin molecules in fibrils display an average end-to-end distance of ∼133 nm. Sampling of site-specific antibody epitopes along the thinnest fibrils (protofibrils) shows periodic punctate label patterns with ∼95 nm repeats and alternating N- and C-terminal regions. These measurements suggest an antiparallel 30-40 nm overlap between N-termini, suggesting that the first five type I modules bind type III modules of the adjacent molecule. Thicker fibres show random bundling of protofibrils without a well-defined line-up. This super-resolution microscopy approach can be applied to other fibrillar protein assemblies of unknown structure.
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich 8093, Switzerland.
authors.forename: Susanna Maria
authors.initials: SM
authors.lastname: Früh
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich 8093, Switzerland.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Schoen
authors.affiliation: European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Ries
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich 8093, Switzerland.
authors.forename: Viola
authors.initials: V
authors.lastname: Vogel
mesh_terms: D005109:Extracellular Matrix / Q000737:chemistry / Q000648:ultrastructure*; D005353:Fibronectins / Q000737:chemistry / Q000648:ultrastructure*; D006801:Humans; D061848:Optical Imaging; D038761:Photobleaching; D011487:Protein Conformation
chemical_list: D005353:Fibronectins