Fast-folding α-helices as reversible strain absorbers in the muscle protein myomesin

Felix Berkemeier, Morten Bertz, Senbo Xiao, Nikos Pinotsis, Matthias Wilmanns, Frauke Gräter, Matthias Rief*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


The highly oriented filamentous protein network of muscle constantly experiences significant mechanical load during muscle operation. The dimeric protein myomesin has been identified as an important M-band component supporting the mechanical integrity of the entire sarcomere. Recent structural studies have revealed a long α-helical linker between the C-terminal immunoglobulin (Ig) domains My12 and My13 of myomesin. In this paper, we have used single-molecule force spectroscopy in combination with molecular dynamics simulations to characterize the mechanics of the myomesin dimer comprising immunoglobulin domains My12-My13. We find that at forces of approximately 30 pN the α-helical linker reversibly elongates allowing the molecule to extend by more than the folded extension of a full domain. High-resolution measurements directly reveal the equilibrium folding/ unfolding kinetics of the individual helix. We show that α-helix unfolding mechanically protects the molecule homodimerization from dissociation at physiologically relevant forces. As fast and reversible molecular springs the myomesin α-helical linkers are an essential component for the structural integrity of the M band.

Original languageEnglish
Pages (from-to)14139-14144
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number34
Publication statusPublished - 2011 Aug 23


  • Atomic force microscopy
  • Protein folding

ASJC Scopus subject areas

  • General


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