Tropomyosin position on F-actin revealed by EM reconstruction and computational chemistry
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Authors
Li, Xiachuan EdwardTobacman, Larry S.
Mun, Ji Young
Craig, Roger W.
Fischer, Stefan
Lehman, William
UMass Chan Affiliations
Department of Cell BiologyDocument Type
Journal ArticlePublication Date
2011-02-16Keywords
ActinsAmino Acids
Animals
*Computer Simulation
Image Processing, Computer-Assisted
Imaging, Three-Dimensional
Microscopy, Electron
Models, Molecular
Protein Binding
Rabbits
Reproducibility of Results
Static Electricity
Tropomyosin
Cell Biology
Metadata
Show full item recordAbstract
Electron microscopy and fiber diffraction studies of reconstituted F-actin-tropomyosin filaments reveal the azimuthal position of end-to-end linked tropomyosin molecules on the surface of actin. However, the longitudinal z-position of tropomyosin along F-actin is still uncertain. Without this information, atomic models of F-actin-tropomyosin filaments, free of constraints imposed by troponin or other actin-binding proteins, cannot be formulated, and thus optimal interfacial contacts between actin and tropomyosin remain unknown. Here, a computational search assessing electrostatic interactions for multiple azimuthal locations, z-positions, and pseudo-rotations of tropomyosin on F-actin was performed. The information gleaned was used to localize tropomyosin on F-actin, yielding an atomic model characterized by protein-protein contacts that primarily involve clusters of basic amino acids on actin subdomains 1 and 3 juxtaposed against acidic residues on the successive quasi-repeating units of tropomyosin. A virtually identical model generated by docking F-actin and tropomyosin atomic structures into electron microscopy reconstructions of F-actin-tropomyosin validated the above solution. Here, the z-position of tropomyosin alongside F-actin was defined by matching the seven broad and narrow motifs that typify tropomyosin's twisting superhelical coiled-coil to the wide and tapering tropomyosin densities seen in surface views of F-actin-tropomyosin reconstructions. The functional implications of the F-actin-tropomyosin models determined in this work are discussed. rights reserved.Source
Biophys J. 2011 Feb 16;100(4):1005-13. Link to article on publisher's siteDOI
10.1016/j.bpj.2010.12.3697Permanent Link to this Item
http://hdl.handle.net/20.500.14038/26424PubMed ID
21320445Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1016/j.bpj.2010.12.3697