Distribution and evolution of stable single α-helices (SAH domains) in myosin motor proteins

PLoS One. 2017 Apr 3;12(4):e0174639. doi: 10.1371/journal.pone.0174639. eCollection 2017.


Stable single-alpha helices (SAHs) are versatile structural elements in many prokaryotic and eukaryotic proteins acting as semi-flexible linkers and constant force springs. This way SAH-domains function as part of the lever of many different myosins. Canonical myosin levers consist of one or several IQ-motifs to which light chains such as calmodulin bind. SAH-domains provide flexibility in length and stiffness to the myosin levers, and may be particularly suited for myosins working in crowded cellular environments. Although the function of the SAH-domains in human class-6 and class-10 myosins has well been characterised, the distribution of the SAH-domain in all myosin subfamilies and across the eukaryotic tree of life remained elusive. Here, we analysed the largest available myosin sequence dataset consisting of 7919 manually annotated myosin sequences from 938 species representing all major eukaryotic branches using the SAH-prediction algorithm of Waggawagga, a recently developed tool for the identification of SAH-domains. With this approach we identified SAH-domains in more than one third of the supposed 79 myosin subfamilies. Depending on the myosin class, the presence of SAH-domains can range from a few to almost all class members indicating complex patterns of independent and taxon-specific SAH-domain gain and loss.

MeSH terms

  • Algorithms
  • Amino Acid Sequence
  • Animals
  • Calmodulin / metabolism
  • Drosophila
  • Humans
  • Myosins / metabolism*
  • Protein Binding
  • Protein Conformation, alpha-Helical / physiology*
  • Protein Domains / physiology*


  • Calmodulin
  • Myosins

Grants and funding

KH performed all work related to this manuscript when he was affiliated at the Max-Planck-Institute for Biophysical Chemistry. He is now working at F. Hoffmann-La Roche Ltd. (current address). Hoffmann-La Roche did not have any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.