Title | α-Helix Unwinding as Force Buffer in Spectrins. |
Publication Type | Journal Article |
Year of Publication | 2018 |
Authors | Takahashi H, Rico F, Chipot C, Scheuring S |
Journal | ACS Nano |
Volume | 12 |
Issue | 3 |
Pagination | 2719-2727 |
Date Published | 2018 Mar 27 |
ISSN | 1936-086X |
Abstract | Spectrins are cytoskeletal proteins located at the inner face of the plasma membrane, making connections between membrane anchors and the actin cortex, and between actin filaments. Spectrins share a common structure forming a bundle of 3 α-helices and play a major role during cell deformation. Here, we used high-speed force spectroscopy and steered molecular dynamics simulations to understand the mechanical stability of spectrin, revealing a molecular force buffering function. We find that spectrin acts as a soft spring at short extensions (70-100 Å). Under continuous external stretching, its α-helices unwind, leading to a viscous mechanical response over larger extensions (100-300 Å), represented by a constant-force plateau in force/extension curves. This viscous force buffering emerges from a quasi-equilibrium competition between disruption and re-formation of α-helical hydrogen bonds. Our results suggest that, in contrast to β-sheet proteins, which unfold in a catastrophic event, α-helical spectrins dominantly unwind, providing a viscous force buffer over extensions about 5 times their folded length. |
DOI | 10.1021/acsnano.7b08973 |
Alternate Journal | ACS Nano |
PubMed ID | 29390177 |