title: Conserved segments 1A and 2B of the intermediate filament dimer: their atomic structures and role in filament assembly.
abstract: Intermediate filaments (IFs) are key components of the cytoskeleton in higher eukaryotic cells. The elementary IF 'building block' is an elongated coiled-coil dimer consisting of four consecutive alpha-helical segments. The segments 1A and 2B include highly conserved sequences and are critically involved in IF assembly. Based on the crystal structures of three human vimentin fragments at 1.4-2.3 A resolution (PDB entries 1gk4, 1gk6 and 1gk7), we have established the molecular organization of these two segments. The fragment corresponding to segment 1A forms a single, amphipatic alpha-helix, which is compatible with a coiled-coil geometry. While this segment might yield a coiled coil within an isolated dimer, monomeric 1A helices are likely to play a role in specific dimer-dimer interactions during IF assembly. The 2B segment reveals a double-stranded coiled coil, which unwinds near residue Phe351 to accommodate a 'stutter'. A fragment containing the last seven heptads of 2B interferes heavily with IF assembly and also transforms mature vimentin filaments into a new kind of structure. These results provide the first insight into the architecture and functioning of IFs at the atomic level.
authors.affiliation: Maurice E.Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland. sergei-v.strelkov@unibas.ch
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Strelkov
authors.forename: Harald
authors.initials: H
authors.lastname: Herrmann
authors.forename: Norbert
authors.initials: N
authors.lastname: Geisler
authors.forename: Tatjana
authors.initials: T
authors.lastname: Wedig
authors.forename: Ralf
authors.initials: R
authors.lastname: Zimbelmann
authors.forename: Ueli
authors.initials: U
authors.lastname: Aebi
authors.forename: Peter
authors.initials: P
authors.lastname: Burkhard
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D014746:Vimentin / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology
chemical_list: D014746:Vimentin