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High-speed AFM reveals subsecond dynamics of cardiac thin filaments upon Ca2+ activation and heavy meromyosin binding
McGill Univ, Canada.ORCID iD: 0000-0002-0824-9260
Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.ORCID iD: 0000-0002-5889-7792
Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences. McGill Univ, Canada.ORCID iD: 0000-0003-2819-3046
McGill Univ, Canada.
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2019 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 33, p. 16384-16393Article in journal (Refereed) Published
Abstract [en]

High-speed atomic force microscopy (HS-AFM) can be used to study dynamic processes with real-time imaging of molecules within 1- to 5-nm spatial resolution. In the current study, we evaluated the 3-state model of activation of cardiac thin filaments (cTFs) isolated as a complex and deposited on a mica-supported lipid bilayer. We studied this complex for dynamic conformational changes 1) at low and high [Ca2+] (pCa 9.0 and 4.5), and 2) upon myosin binding to the cTF in the nucleotide-free state or in the presence of ATP. HS-AFM was used to directly visualize the tropo-myosin-troponin complex and Ca2+-induced tropomyosin movements accompanied by structural transitions of actin monomers within cTFs. Our data show that cTFs at relaxing or activating conditions are not ultimately in a blocked or activated state, respectively, but rather the combination of states with a prevalence that is dependent on the [Ca2+] and the presence of weakly or strongly bound myosin. The weakly and strongly bound myosin induce similar changes in the structure of cTFs as confirmed by the local dynamical displacement of individual tropomyosin strands in the center of a regulatory unit of cTF at the relaxed and activation conditions. The displacement of tropomyosin at the relaxed conditions had never been visualized directly and explains the ability of myosin binding to TF at the relaxed conditions. Based on the ratios of nonactivated and activated segments within cTFs, we proposed a mechanism of tropomyosin switching from different states that includes both weakly and strongly bound myosin.

Place, publisher, year, edition, pages
National Academy of Sciences , 2019. Vol. 116, no 33, p. 16384-16393
Keywords [en]
thin filaments, muscle contraction, HS-AFM
National Category
Biophysics Biochemistry and Molecular Biology
Research subject
Chemistry, Biochemistry
Identifiers
URN: urn:nbn:se:lnu:diva-88826DOI: 10.1073/pnas.1903228116ISI: 000481404300041PubMedID: 31358631OAI: oai:DiVA.org:lnu-88826DiVA, id: diva2:1346971
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29Bibliographically approved

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Månsson, AlfPersson, Malin

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Matusovsky, Oleg S.Månsson, AlfPersson, Malin
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