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Huang X, Torre I, Chiappi M, Yin Z, Vydyanath A, Cao S, Raschdorf O, Beeby M, Quigley B, de Tombe PP, Liu J, Morris EP, Luther PK. Cryo-electron tomography of intact cardiac muscle reveals myosin binding protein-C linking myosin and actin filaments. J Muscle Res Cell Motil 2023; 44:165-178. [PMID: 37115473 PMCID: PMC10542292 DOI: 10.1007/s10974-023-09647-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 03/29/2023] [Indexed: 04/29/2023]
Abstract
Myosin binding protein C (MyBP-C) is an accessory protein of the thick filament in vertebrate cardiac muscle arranged over 9 stripes of intervals of 430 Å in each half of the A-band in the region called the C-zone. Mutations in cardiac MyBP-C are a leading cause of hypertrophic cardiomyopathy the mechanism of which is unknown. It is a rod-shaped protein composed of 10 or 11 immunoglobulin- or fibronectin-like domains labelled C0 to C10 which binds to the thick filament via its C-terminal region. MyBP-C regulates contraction in a phosphorylation dependent fashion that may be through binding of its N-terminal domains with myosin or actin. Understanding the 3D organisation of MyBP-C in the sarcomere environment may provide new light on its function. We report here the fine structure of MyBP-C in relaxed rat cardiac muscle by cryo-electron tomography and subtomogram averaging of refrozen Tokuyasu cryosections. We find that on average MyBP-C connects via its distal end to actin across a disc perpendicular to the thick filament. The path of MyBP-C suggests that the central domains may interact with myosin heads. Surprisingly MyBP-C at Stripe 4 is different; it has weaker density than the other stripes which could result from a mainly axial or wavy path. Given that the same feature at Stripe 4 can also be found in several mammalian cardiac muscles and in some skeletal muscles, our finding may have broader implication and significance. In the D-zone, we show the first demonstration of myosin crowns arranged on a uniform 143 Å repeat.
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Affiliation(s)
- Xinrui Huang
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, 100191, China
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT, 06516, USA
| | - Iratxe Torre
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
| | - Michele Chiappi
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
| | - Zhan Yin
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
| | - Anupama Vydyanath
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
| | - Shuangyi Cao
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
| | | | - Morgan Beeby
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Bonnie Quigley
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Pieter P de Tombe
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 S. Wolcott Ave, Chicago, IL, 60612, USA
- Phymedexp, Université de Montpellier, Inserm, CNRS, Montpellier, France
| | - Jun Liu
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT, 06516, USA
| | - Edward P Morris
- Division of Structural Biology, Institute of Cancer Research, London, SW3 6JB, UK
- School of Molecular Biosciences, University of Glasgow, Garscube Campus, Jarrett Building, 351, Bearsden Road, Glasgow, G61 1QH, UK
| | - Pradeep K Luther
- National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK.
- Cardiac Function Section, National Heart and Lung Institute, Imperial College London, London, SW7 2AZ, UK.
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Alamo L, Koubassova N, Pinto A, Gillilan R, Tsaturyan A, Padrón R. Lessons from a tarantula: new insights into muscle thick filament and myosin interacting-heads motif structure and function. Biophys Rev 2017; 9:461-480. [PMID: 28871556 DOI: 10.1007/s12551-017-0295-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/27/2017] [Indexed: 12/13/2022] Open
Abstract
The tarantula skeletal muscle X-ray diffraction pattern suggested that the myosin heads were helically arranged on the thick filaments. Electron microscopy (EM) of negatively stained relaxed tarantula thick filaments revealed four helices of heads allowing a helical 3D reconstruction. Due to its low resolution (5.0 nm), the unambiguous interpretation of densities of both heads was not possible. A resolution increase up to 2.5 nm, achieved by cryo-EM of frozen-hydrated relaxed thick filaments and an iterative helical real space reconstruction, allowed the resolving of both heads. The two heads, "free" and "blocked", formed an asymmetric structure named the "interacting-heads motif" (IHM) which explained relaxation by self-inhibition of both heads ATPases. This finding made tarantula an exemplar system for thick filament structure and function studies. Heads were shown to be released and disordered by Ca2+-activation through myosin regulatory light chain phosphorylation, leading to EM, small angle X-ray diffraction and scattering, and spectroscopic and biochemical studies of the IHM structure and function. The results from these studies have consequent implications for understanding and explaining myosin super-relaxed state and thick filament activation and regulation. A cooperative phosphorylation mechanism for activation in tarantula skeletal muscle, involving swaying constitutively Ser35 mono-phosphorylated free heads, explains super-relaxation, force potentiation and post-tetanic potentiation through Ser45 mono-phosphorylated blocked heads. Based on this mechanism, we propose a swaying-swinging, tilting crossbridge-sliding filament for tarantula muscle contraction.
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Affiliation(s)
- Lorenzo Alamo
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela
| | - Natalia Koubassova
- Institute of Mechanics, Moscow State University, Mitchurinsky prosp. 1, Moscow, 119992, Russia
| | - Antonio Pinto
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela
| | - Richard Gillilan
- Macromolecular Diffraction Facility, Cornell High Energy Synchrotron Source, Ithaca, NY, USA
| | - Andrey Tsaturyan
- Institute of Mechanics, Moscow State University, Mitchurinsky prosp. 1, Moscow, 119992, Russia
| | - Raúl Padrón
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
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