title: Stable single α-helices are constant force springs in proteins.
abstract: Single α-helix (SAH) domains are rich in charged residues (Arg, Lys, and Glu) and stable in solution over a wide range of pH and salt concentrations. They are found in many different proteins where they bridge two functional domains. To test the idea that their high stability might enable these proteins to resist unfolding along their length, the properties and unfolding behavior of the predicted SAH domain from myosin-10 were characterized. The expressed and purified SAH domain was highly helical, melted non-cooperatively, and was monomeric as shown by circular dichroism and mass spectrometry as expected for a SAH domain. Single molecule force spectroscopy experiments showed that the SAH domain unfolded at very low forces (<30 pN) without a characteristic unfolding peak. Molecular dynamics simulations showed that the SAH domain unfolds progressively as the length is increased and refolds progressively as the length is reduced. This enables the SAH domain to act as a constant force spring in the mechanically dynamic environment of the cell.
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Marcin
authors.initials: M
authors.lastname: Wolny
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Batchelor
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Knight
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Paci
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Lorna
authors.initials: L
authors.lastname: Dougan
authors.affiliation: From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom m.peckham@leeds.ac.uk.
authors.forename: Michelle
authors.initials: M
authors.lastname: Peckham
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D009218:Myosins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D009218:Myosins
keywords: Atomic Force Microscopy (AFM); Circular Dichroism (CD); Cytoskeleton; Molecular Dynamics; Single α-Helices; Structural Biology