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Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
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 cooperativ...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
eLife Sciences Publications, Ltd
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476120/ https://www.ncbi.nlm.nih.gov/pubmed/34569933 http://dx.doi.org/10.7554/eLife.69184 |
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author | Smith, Quentin M Inchingolo, Alessio V Mihailescu, Madalina-Daniela Dai, Hongsheng Kad, Neil M |
author_facet | Smith, Quentin M Inchingolo, Alessio V Mihailescu, Madalina-Daniela Dai, Hongsheng Kad, Neil M |
author_sort | Smith, Quentin M |
collection | PubMed |
description | 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. |
format | Online Article Text |
id | pubmed-8476120 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | eLife Sciences Publications, Ltd |
record_format | MEDLINE/PubMed |
spelling | pubmed-84761202021-09-29 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 eLife Biochemistry and Chemical Biology 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. eLife Sciences Publications, Ltd 2021-09-27 /pmc/articles/PMC8476120/ /pubmed/34569933 http://dx.doi.org/10.7554/eLife.69184 Text en © 2021, Smith et al https://creativecommons.org/licenses/by/4.0/This article is distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use and redistribution provided that the original author and source are credited. |
spellingShingle | Biochemistry and Chemical Biology Smith, Quentin M Inchingolo, Alessio V Mihailescu, Madalina-Daniela Dai, Hongsheng Kad, Neil M Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title | Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title_full | Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title_fullStr | Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title_full_unstemmed | Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title_short | Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
title_sort | single-molecule imaging reveals the concerted release of myosin from regulated thin filaments |
topic | Biochemistry and Chemical Biology |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476120/ https://www.ncbi.nlm.nih.gov/pubmed/34569933 http://dx.doi.org/10.7554/eLife.69184 |
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