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Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments

Smith, Quentin M, Inchingolo, Alessio V, Mihailescu, Madalina-Daniela, Dai, Hongsheng, Kad, Neil M (2021) Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments. eLife, . Article Number e69184. ISSN 2050-084X. (doi:10.7554/eLife.69184) (KAR id:90476)

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Regulated thin filaments (RTFs) tightly control striated muscle contraction through calcium binding to troponin, which enables tropomyosin to expose myosin-binding sites on actin. Myosin binding holds tropomyosin in an open position, exposing more myosin-binding sites on actin, leading to cooperative activation. At lower calcium levels, troponin and tropomyosin turn off the thin filament; however, this is antagonised by the high local concentration of myosin, questioning how the thin filament relaxes. To provide molecular details of deactivation, we used single-molecule imaging of green fluorescent protein (GFP)-tagged myosin-S1 (S1-GFP) to follow the activation of RTF tightropes. In sub-maximal activation conditions, RTFs are not fully active, enabling direct observation of deactivation in real time. We observed that myosin binding occurs in a stochastic step-wise fashion; however, an unexpectedly large probability of multiple contemporaneous detachments is observed. This suggests that deactivation of the thin filament is a coordinated active process.

Item Type: Article
DOI/Identification number: 10.7554/eLife.69184
Uncontrolled keywords: Regulated thin filmanets, RTFs, myosin
Subjects: Q Science > QD Chemistry > QD431 Organic Chemistry- Biochemistry- Proteins, peptides, amino acids
Divisions: Divisions > Division of Natural Sciences > Biosciences
Depositing User: Neil Kad
Date Deposited: 29 Sep 2021 16:17 UTC
Last Modified: 14 Nov 2022 23:13 UTC
Resource URI: (The current URI for this page, for reference purposes)
Kad, Neil M:
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