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Structural basis underlying specific biochemical activities of non-muscle tropomyosin isoforms. | LitMetric

Structural basis underlying specific biochemical activities of non-muscle tropomyosin isoforms.

Cell Rep

Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland. Electronic address:

Published: January 2023

AI Article Synopsis

  • - The actin cytoskeleton is essential for various cellular functions like cell movement, shape change, and division, with actin filaments having different structures to support these processes
  • - Tropomyosin proteins play a crucial role in regulating the behavior of actin filaments and interacting with other proteins, but the details of how they function together have not been fully understood
  • - By using cryogenic electron microscopy, researchers discovered that two types of tropomyosin (Tpm1.6 and Tpm3.2) bind to actin filaments without changing their shape, but take different paths along the filament, explaining their distinct roles in activating myosin and preventing the breakdown of actin filaments by other proteins.

Article Abstract

The actin cytoskeleton is critical for cell migration, morphogenesis, endocytosis, organelle dynamics, and cytokinesis. To support diverse cellular processes, actin filaments form a variety of structures with specific architectures and dynamic properties. Key proteins specifying actin filaments are tropomyosins. Non-muscle cells express several functionally non-redundant tropomyosin isoforms, which differentially control the interactions of other proteins, including myosins and ADF/cofilin, with actin filaments. However, the underlying molecular mechanisms have remained elusive. By determining the cryogenic electron microscopy structures of actin filaments decorated by two functionally distinct non-muscle tropomyosin isoforms, Tpm1.6 and Tpm3.2, we reveal that actin filament conformation remains unaffected upon binding. However, Tpm1.6 and Tpm3.2 follow different paths along the actin filament major groove, providing an explanation for their incapability to co-polymerize on actin filaments. We also elucidate the molecular basis underlying specific roles of Tpm1.6 and Tpm3.2 in myosin II activation and protecting actin filaments from ADF/cofilin-catalyzed severing.

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Source
http://dx.doi.org/10.1016/j.celrep.2022.111900DOI Listing

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