Molecular basis of F-actin regulation and sarcomere assembly via myotilin

PLoS Biol. 2021 Apr 12;19(4):e3001148. doi: 10.1371/journal.pbio.3001148. eCollection 2021 Apr.


Sarcomeres, the basic contractile units of striated muscle cells, contain arrays of thin (actin) and thick (myosin) filaments that slide past each other during contraction. The Ig-like domain-containing protein myotilin provides structural integrity to Z-discs-the boundaries between adjacent sarcomeres. Myotilin binds to Z-disc components, including F-actin and α-actinin-2, but the molecular mechanism of binding and implications of these interactions on Z-disc integrity are still elusive. To illuminate them, we used a combination of small-angle X-ray scattering, cross-linking mass spectrometry, and biochemical and molecular biophysics approaches. We discovered that myotilin displays conformational ensembles in solution. We generated a structural model of the F-actin:myotilin complex that revealed how myotilin interacts with and stabilizes F-actin via its Ig-like domains and flanking regions. Mutant myotilin designed with impaired F-actin binding showed increased dynamics in cells. Structural analyses and competition assays uncovered that myotilin displaces tropomyosin from F-actin. Our findings suggest a novel role of myotilin as a co-organizer of Z-disc assembly and advance our mechanistic understanding of myotilin's structural role in Z-discs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / chemistry
  • Actin Cytoskeleton / genetics
  • Actin Cytoskeleton / metabolism
  • Actins / chemistry
  • Actins / genetics
  • Actins / metabolism*
  • Animals
  • Cells, Cultured
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Cytoskeleton / metabolism
  • Humans
  • Mice
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Muscle Contraction / genetics
  • Muscle, Skeletal / metabolism
  • Protein Binding / genetics
  • Protein Interaction Domains and Motifs / genetics
  • Protein Multimerization* / genetics
  • Sarcomeres / genetics
  • Sarcomeres / metabolism*
  • Tropomyosin / chemistry
  • Tropomyosin / genetics
  • Tropomyosin / metabolism


  • Actins
  • Cytoskeletal Proteins
  • Microfilament Proteins
  • Myot protein, mouse
  • Tropomyosin