Muscular movement plays an essential role not only in our lives but also describes a fundamental mechanism of force production. Filamentous actin (F-actin) is the major protein of muscle thin filaments, and actin microfilaments are the main component of the eukaryotic cytoskeleton. The interaction of myosin with actin filaments is the central feature of muscle contraction and cargo movement along actin filaments. In striated muscle fibres, this interplay is mainly regulated by tropomyosin and troponin. Although crystal structures for monomeric actin are available, the difficulty of obtaining diffracting crystals, however, has prevented structure determination by crystallography of F-actin. High-resolution structures of F-actin in complex are still missing, hampering our understanding of how disease-causing mutations affect the function of thin muscle filaments and affecting skeletal and cardiac muscles.

We solved the three-dimensional structure of F-actin in complex with tropomyosin at a resolution of 3.7 Å (von der Ecken et al., 2015). We used cutting edge transmission electron cryomicroscopy and direct electron detectors and implemented new methods for processing of the data. The structure reveals insights in the inner interaction of the F-actin subunits and the interplay of F-actin and tropomyosin at near-atomic resolution.

Reference:

von der Ecken J., Müller M., Lehman W., Manstein D.J., Penczek P.A., Raunser S. (2015): Structure of the F-actin-tropomyosin complex. Nature 519, 114-117.

Figures:

Cryo-EM stucture of skeletal F-actin-tropomyosin complex at near-atomic resolution.

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EMC Abstracts - https://emc-proceedings.com/abstract/our-muscle-at-near-atomic-resolution-cryo-em-structure-of-the-f-actin-tropomyosin-complex/