title: Nano-mechanical characterization of tension-sensitive helix bundles in talin rod.
abstract: Tension-induced exposure of a cryptic signaling binding site is one of the most fundamental mechanisms in molecular mechanotransduction. Helix bundles in rod domains of talin, a tension-sensing protein at focal adhesions, unfurl under tension to expose cryptic vinculin binding sites. Although the difference in their mechanical stabilities would determine which helix bundle is tension-sensitive, their respective mechanical behaviors under tension have not been characterized. In this study, we evaluated the mechanical behaviors of residues 486-654 and 754-889 of talin, which form helix bundles with low and high tension-sensitivity, by employing AFM nano-tensile testing. As a result, residues 754-889 exhibited lower unfolding energy for complete unfolding than residues 486-654. In addition, we found that residues 754-889 transition into intermediate conformations under lower tension than residues 486-654. Furthermore, residues 754-889 showed shorter persistence length in the intermediate conformation than residues 486-654, suggesting that residues 754-889 under tension exhibit separated α-helices, while residues 486-654 assume a compact conformation with inter-helix interactions. Therefore, we suggest that residues 754-889 of talin work as a tension-sensitive domain to recruit vinculin at the early stage of focal adhesion development, while residues 486-654 contribute to rather robust tension-sensitivity by recruiting vinculin under high tension.
authors.affiliation: Laboratory of Biomechanics, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto 606-8507, Japan; Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Maki
authors.affiliation: Laboratory of Biomechanics, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto 606-8507, Japan; Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan.
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Nakao
authors.affiliation: Laboratory of Biomechanics, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto 606-8507, Japan; Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan. Electronic address: adachi@frontier.kyoto-u.ac.jp.
authors.forename: Taiji
authors.initials: T
authors.lastname: Adachi
mesh_terms: D018625:Microscopy, Atomic Force; D036103:Nanotechnology; D011487:Protein Conformation; D016608:Talin / Q000737:chemistry*; D013718:Tensile Strength
chemical_list: D016608:Talin
keywords: Atomic force microscopy (AFM); Helix bundle; Mechanotransduction; Nano-tensile testing; Talin; Vinculin