In Vitro Assembly Kinetics of Cytoplasmic Intermediate Filaments: A Correlative Monte Carlo Simulation Study.
Intermediate filament (IF) elongation proceeds via full-width "mini-filaments", referred to as "unit-length" filaments (ULFs), which instantaneously form by lateral association of extended coiled-coil complexes after assembly is initiated. In a comparatively much slower process, ULFs longitudinally interact end-to-end with other ULFs to form short filaments, which further anneal with ULFs and with each other to increasingly longer filaments. This assembly concept was derived from time-lapse electron and atomic force microscopy data. We previously have quantitatively verified this concept through the generation of time-dependent filament length-profiles and an analytical model that describes assembly kinetics well for about the first ten minutes. In this time frame, filaments are shorter than one persistence length, i.e. ~1 μm, and thus filaments were treated as stiff rods associating via their ends. However, when filaments grow several μm in length over hours, their flexibility becomes a significant factor for the kinetics of the longitudinal annealing process. Incorporating now additional filament length distributions that we have recorded after extended assembly times by total internal reflection fluorescence microscopy (TIRFM), we developed a Monte Carlo simulation procedure that accurately describes the underlying assembly kinetics for large time scales.
Division Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Norbert
N
Mücke
Division Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Stefan
S
Winheim
Department of Physics and ITPA, Xiamen University, Xiamen, China.
Holger
H
Merlitz
Division Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Jan
J
Buchholz
Division Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Jörg
J
Langowski
Institute of Neuropathology, University Hospital Erlangen, Erlangen, Germany.
Harald
H
Herrmann
D000465:Algorithms; D003593:Cytoplasm / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D003893:Desmin / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism* / Q000648:ultrastructure; D053538:Keratin-18 / Q000378:metabolism* / Q000648:ultrastructure; D053533:Keratin-8 / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009010:Monte Carlo Method; D013997:Time Factors; D059008:Time-Lapse Imaging / Q000379:methods; D014746:Vimentin / Q000378:metabolism* / Q000648:ultrastructure
D003893:Desmin; D053538:Keratin-18; D053533:Keratin-8; D014746:Vimentin