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Talukdar D, Gole B. Foldamer-Based Mechanoresponsive Materials: Molecular Nanoarchitectonics to Advanced Functions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 39051976 DOI: 10.1021/acs.langmuir.4c01252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
Artificial molecules that respond to external stimuli such as light, heat, chemical signals, and mechanical force have garnered significant interest due to their tunable functions, variable optical properties, and mechanical responses. Particularly, mechanoresponsive materials featuring molecules that respond to mechanical stress or show force-induced optical changes have been intriguing due to their extraordinary functions. Despite the promising potential of many such materials reported in the past, practical applications have remained limited, primarily because their functions often depend on irreversible covalent bond rupture. Foldamers, oligomers that fold into well-defined secondary structures, offer an alternative class of mechanoactive motifs. These molecules can reversibly sustain mechanical stress and efficiently dissipate energy by transitioning between folded and unfolded states. This review focuses on the emerging properties of foldamer-based mechanoresponsive materials. We begin by highlighting the mechanical responses of foldamers in their molecular form, which have been primarily investigated using single-molecule force spectroscopy and other analytical methods. Following this, we provide a detailed survey of the current trends in foldamer-appended polymers, emphasizing their emerging mechanical and mechanochromic properties. Subsequently, we present an overview of the state-of-the-art advancements in foldamer-appended polymers, showcasing significant reports in this field. This review covers some of the most recent advances in this direction and draws a perspective for further development.
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Affiliation(s)
- Dhrubajyoti Talukdar
- Biomimetic Supramolecular Chemistry Laboratory, Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Greater Noida, Uttar Pradesh 201314, India
| | - Bappaditya Gole
- Biomimetic Supramolecular Chemistry Laboratory, Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Greater Noida, Uttar Pradesh 201314, India
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2
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Beedle AEM, Garcia-Manyes S. The role of single protein elasticity in mechanobiology. NATURE REVIEWS. MATERIALS 2023; 8:10-24. [PMID: 37469679 PMCID: PMC7614781 DOI: 10.1038/s41578-022-00488-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 09/07/2022] [Indexed: 07/21/2023]
Abstract
In addition to biochemical signals and genetic considerations, mechanical forces are rapidly emerging as a master regulator of human physiology. Yet the molecular mechanisms that regulate force-induced functionalities across a wide range of scales, encompassing the cell, tissue or organ levels, are comparatively not so well understood. With the advent, development and refining of single molecule nanomechanical techniques, enabling to exquisitely probe the conformational dynamics of individual proteins under the effect of a calibrated force, we have begun to acquire a comprehensive knowledge on the rich plethora of physicochemical principles that regulate the elasticity of single proteins. Here we review the major advances underpinning our current understanding of how the elasticity of single proteins regulates mechanosensing and mechanotransduction. We discuss the present limitations and future challenges of such a prolific and burgeoning field.
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Affiliation(s)
- Amy EM Beedle
- Department of Physics, Randall Centre for Cell and Molecular Biophysics, Centre for the Physical Science of Life and London Centre for Nanotechnology, King’s College London, Strand, WC2R 2LS London, United Kingdom
- Institute for Bioengineering of Catalonia (IBEC), the Barcelona Institute of Technology (BIST), 08028 Barcelona, Spain
| | - Sergi Garcia-Manyes
- Department of Physics, Randall Centre for Cell and Molecular Biophysics, Centre for the Physical Science of Life and London Centre for Nanotechnology, King’s College London, Strand, WC2R 2LS London, United Kingdom
- Single Molecule Mechanobiology Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, London, UK
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3
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Goult BT, von Essen M, Hytönen VP. The mechanical cell - the role of force dependencies in synchronising protein interaction networks. J Cell Sci 2022; 135:283155. [PMID: 36398718 PMCID: PMC9845749 DOI: 10.1242/jcs.259769] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The role of mechanical signals in the proper functioning of organisms is increasingly recognised, and every cell senses physical forces and responds to them. These forces are generated both from outside the cell or via the sophisticated force-generation machinery of the cell, the cytoskeleton. All regions of the cell are connected via mechanical linkages, enabling the whole cell to function as a mechanical system. In this Review, we define some of the key concepts of how this machinery functions, highlighting the critical requirement for mechanosensory proteins, and conceptualise the coupling of mechanical linkages to mechanochemical switches that enables forces to be converted into biological signals. These mechanical couplings provide a mechanism for how mechanical crosstalk might coordinate the entire cell, its neighbours, extending into whole collections of cells, in tissues and in organs, and ultimately in the coordination and operation of entire organisms. Consequently, many diseases manifest through defects in this machinery, which we map onto schematics of the mechanical linkages within a cell. This mapping approach paves the way for the identification of additional linkages between mechanosignalling pathways and so might identify treatments for diseases, where mechanical connections are affected by mutations or where individual force-regulated components are defective.
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Affiliation(s)
- Benjamin T. Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, Kent, UK,Authors for correspondence (; )
| | - Magdaléna von Essen
- Faculty of Medicine and Health Technology, Tampere University, FI-33100 Tampere, Finland
| | - Vesa P. Hytönen
- Faculty of Medicine and Health Technology, Tampere University, FI-33100 Tampere, Finland,Fimlab Laboratories, FI-33520 Tampere, Finland,Authors for correspondence (; )
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4
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Kang K, Zhou N, Peng W, Peng F, Ma M, Li L, Fu F, Xiang S, Zhang H, He X, Song Z. Multi-Omics Analysis of the Microbiome and Metabolome Reveals the Relationship Between the Gut Microbiota and Wooden Breast Myopathy in Broilers. Front Vet Sci 2022; 9:922516. [PMID: 35812872 PMCID: PMC9260154 DOI: 10.3389/fvets.2022.922516] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 05/23/2022] [Indexed: 11/19/2022] Open
Abstract
Wooden breast (WB) is a widely prevalent myopathy in broiler chickens. However, the role of the gut microbiota in this myopathy remains largely unknown, in particular the regulatory effect of gut microbiota in the modulation of muscle metabolism. Totally, 300 1-day-old Arbor Acres broilers were raised until 49 days and euthanized, and the breast filets were classified as normal (NORM), mild (MILD), or severe wooden breast (SEV). Birds with WB comprised 27.02% of the individuals. Severe WB filets had a greater L* value, a* value, and dripping loss but a lower pH (P < 0.05). WB filets had abundant myofiber fragmentation, with a lower average myofiber caliber and more fibers with a diameter of <20 μm (P < 0.05). The diversity of the intestinal microflora was decreased in birds with severe WB, with decreases in Chao 1, and observed species indices. At the phylum level, birds with severe WB had a lower Firmicutes/Bacteroidetes ratio (P = 0.098) and a decreased abundance of Verrucomicrobia (P < 0.05). At the species level, gut microbiota were positively correlated with 131 digesta metabolites in pathways of glutamine and glutamate metabolism and arginine biosynthesis but were negatively correlated with 30 metabolites in the pathway of tyrosine metabolism. In plasma, WB induced five differentially expressed metabolites (DEMs), including anserine and choline, which were related to the severity of the WB lesion. The microbial-derived metabolites, including guanidoacetic acid, antiarol, and (2E)-decenoyl-ACP, which entered into plasma were related to meat quality traits and myofiber traits. In summary, WB filets differed in gut microbiota, digesta, and plasma metabolites. Gut microbiota respond to the wooden breast myopathy by driving dynamic changes in digesta metabolites that eventually enter the plasma.
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Affiliation(s)
- Kelang Kang
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Nanxuan Zhou
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Weishi Peng
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Fang Peng
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Mengmeng Ma
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Liwei Li
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Fuyi Fu
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Shuhan Xiang
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
| | - Haihan Zhang
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
- Hunan Engineering Research Center of Poultry Production Safety, Changsha, China
| | - Xi He
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
- Hunan Engineering Research Center of Poultry Production Safety, Changsha, China
- Hunan Co-Innovation Center of Animal Production Safety, Changsha, China
| | - Zehe Song
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
- Ministry of Education Engineering Research Center of Feed Safety and Efficient Use, Changsha, China
- Hunan Engineering Research Center of Poultry Production Safety, Changsha, China
- Hunan Co-Innovation Center of Animal Production Safety, Changsha, China
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5
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Abstract
Polymer chains, if long enough, are known to undergo bond scission when mechanically stressed. While the mechanochemical response of random coils is well understood, biopolymers and some key synthetic chains adopt well-defined secondary structures such as helices. To understand covalent mechanochemistry in such structures, poly(γ-benzyl glutamates) are prepared while regulating the feed-monomer chirality, producing chains with similar molecular weights and backbone chemistry but different helicities. Such chains are stressed in solution and their mechanochemistry rates compared by following molecular weight change and using a rhodamine mechanochromophore. Results reveal that while helicity itself is not affected by the covalent bond scissions, chains with higher helicity undergo faster mechanochemistry. Considering that the polymers tested differ only in conformation, these results indicate that helix-induced chain rigidity improves the efficiency of mechanical energy transduction.
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Affiliation(s)
- Hang Zhang
- Schulich Faculty of ChemistryTechnion—Israel Institute of TechnologyHaifa3200008Israel
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6
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Lamber EP, Guicheney P, Pinotsis N. The role of the M-band myomesin proteins in muscle integrity and cardiac disease. J Biomed Sci 2022; 29:18. [PMID: 35255917 PMCID: PMC8900313 DOI: 10.1186/s12929-022-00801-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/28/2022] [Indexed: 11/30/2022] Open
Abstract
Transversal structural elements in cross-striated muscles, such as the M-band or the Z-disc, anchor and mechanically stabilize the contractile apparatus and its minimal unit—the sarcomere. The ability of proteins to target and interact with these structural sarcomeric elements is an inevitable necessity for the correct assembly and functionality of the myofibrillar apparatus. Specifically, the M-band is a well-recognized mechanical and signaling hub dealing with active forces during contraction, while impairment of its function leads to disease and death. Research on the M-band architecture is focusing on the assembly and interactions of the three major filamentous proteins in the region, mainly the three myomesin proteins including their embryonic heart (EH) isoform, titin and obscurin. These proteins form the basic filamentous network of the M-band, interacting with each other as also with additional proteins in the region that are involved in signaling, energetic or mechanosensitive processes. While myomesin-1, titin and obscurin are found in every muscle, the expression levels of myomesin-2 (also known as M-protein) and myomesin-3 are tissue specific: myomesin-2 is mainly expressed in the cardiac and fast skeletal muscles, while myomesin-3 is mainly expressed in intermediate muscles and specific regions of the cardiac muscle. Furthermore, EH-myomesin apart from its role during embryonic stages, is present in adults with specific cardiac diseases. The current work in structural, molecular, and cellular biology as well as in animal models, provides important details about the assembly of myomesin-1, obscurin and titin, the information however about the myomesin-2 and -3, such as their interactions, localization and structural details remain very limited. Remarkably, an increasing number of reports is linking all three myomesin proteins and particularly myomesin-2 to serious cardiovascular diseases suggesting that this protein family could be more important than originally thought. In this review we will focus on the myomesin protein family, the myomesin interactions and structural differences between isoforms and we will provide the most recent evidence why the structurally and biophysically unexplored myomesin-2 and myomesin-3 are emerging as hot targets for understanding muscle function and disease.
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7
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Diesendruck C, Zhang H. Accelerated Mechanochemistry in Helical Polymers. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202115325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Charles Diesendruck
- Technion - Israel Institute of Technology Schulich Faculty of Chemistry Kiryat Hatechnion 3200008 Haifa ISRAEL
| | - Hang Zhang
- Technion Israel Institute of Technology Schulich Faculty of Chemistry Haifa ISRAEL
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8
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Nanosurgical Manipulation of Titin and Its M-Complex. NANOMATERIALS 2022; 12:nano12020178. [PMID: 35055197 PMCID: PMC8779236 DOI: 10.3390/nano12020178] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/01/2022] [Accepted: 01/04/2022] [Indexed: 01/21/2023]
Abstract
Titin is a multifunctional filamentous protein anchored in the M-band, a hexagonally organized supramolecular lattice in the middle of the muscle sarcomere. Functionally, the M-band is a framework that cross-links myosin thick filaments, organizes associated proteins, and maintains sarcomeric symmetry via its structural and putative mechanical properties. Part of the M-band appears at the C-terminal end of isolated titin molecules in the form of a globular head, named here the “M-complex”, which also serves as the point of head-to-head attachment of titin. We used high-resolution atomic force microscopy and nanosurgical manipulation to investigate the topographical and internal structure and local mechanical properties of the M-complex and its associated titin molecules. We find that the M-complex is a stable structure that corresponds to the transverse unit of the M-band organized around the myosin thick filament. M-complexes may be interlinked into an M-complex array that reflects the local structural and mechanical status of the transversal M-band lattice. Local segments of titin and the M-complex could be nanosurgically manipulated to achieve extension and domain unfolding. Long threads could be pulled out of the M-complex, suggesting that it is a compact supramolecular reservoir of extensible filaments. Nanosurgery evoked an unexpected volume increment in the M-complex, which may be related to its function as a mechanical spacer. The M-complex thus displays both elastic and plastic properties which support the idea that the M-band may be involved in mechanical functions within the muscle sarcomere.
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9
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Mechanobiology of muscle and myofibril morphogenesis. Cells Dev 2021; 168:203760. [PMID: 34863916 DOI: 10.1016/j.cdev.2021.203760] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 11/22/2021] [Accepted: 11/22/2021] [Indexed: 01/05/2023]
Abstract
Muscles generate forces for animal locomotion. The contractile apparatus of muscles is the sarcomere, a highly regular array of large actin and myosin filaments linked by gigantic titin springs. During muscle development many sarcomeres assemble in series into long periodic myofibrils that mechanically connect the attached skeleton elements. Thus, ATP-driven myosin forces can power movement of the skeleton. Here we review muscle and myofibril morphogenesis, with a particular focus on their mechanobiology. We describe recent progress on the molecular structure of sarcomeres and their mechanical connections to the skeleton. We discuss current models predicting how tension coordinates the assembly of key sarcomeric components to periodic myofibrils that then further mature during development. This requires transcriptional feedback mechanisms that may help to coordinate myofibril assembly and maturation states with the transcriptional program. To fuel the varying energy demands of muscles we also discuss the close mechanical interactions of myofibrils with mitochondria and nuclei to optimally support powerful or enduring muscle fibers.
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10
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Alegre-Cebollada J. Protein nanomechanics in biological context. Biophys Rev 2021; 13:435-454. [PMID: 34466164 PMCID: PMC8355295 DOI: 10.1007/s12551-021-00822-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/05/2021] [Indexed: 12/20/2022] Open
Abstract
How proteins respond to pulling forces, or protein nanomechanics, is a key contributor to the form and function of biological systems. Indeed, the conventional view that proteins are able to diffuse in solution does not apply to the many polypeptides that are anchored to rigid supramolecular structures. These tethered proteins typically have important mechanical roles that enable cells to generate, sense, and transduce mechanical forces. To fully comprehend the interplay between mechanical forces and biology, we must understand how protein nanomechanics emerge in living matter. This endeavor is definitely challenging and only recently has it started to appear tractable. Here, I introduce the main in vitro single-molecule biophysics methods that have been instrumental to investigate protein nanomechanics over the last 2 decades. Then, I present the contemporary view on how mechanical force shapes the free energy of tethered proteins, as well as the effect of biological factors such as post-translational modifications and mutations. To illustrate the contribution of protein nanomechanics to biological function, I review current knowledge on the mechanobiology of selected muscle and cell adhesion proteins including titin, talin, and bacterial pilins. Finally, I discuss emerging methods to modulate protein nanomechanics in living matter, for instance by inducing specific mechanical loss-of-function (mLOF). By interrogating biological systems in a causative manner, these new tools can contribute to further place protein nanomechanics in a biological context.
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11
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Gazi AD, Kokkinidis M, Fadouloglou VE. α-Helices in the Type III Secretion Effectors: A Prevalent Feature with Versatile Roles. Int J Mol Sci 2021; 22:ijms22115412. [PMID: 34063760 PMCID: PMC8196651 DOI: 10.3390/ijms22115412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/14/2021] [Accepted: 05/17/2021] [Indexed: 12/16/2022] Open
Abstract
Type III Secretion Systems (T3SSs) are multicomponent nanomachines located at the cell envelope of Gram-negative bacteria. Their main function is to transport bacterial proteins either extracellularly or directly into the eukaryotic host cell cytoplasm. Type III Secretion effectors (T3SEs), latest to be secreted T3S substrates, are destined to act at the eukaryotic host cell cytoplasm and occasionally at the nucleus, hijacking cellular processes through mimicking eukaryotic proteins. A broad range of functions is attributed to T3SEs, ranging from the manipulation of the host cell's metabolism for the benefit of the bacterium to bypassing the host's defense mechanisms. To perform this broad range of manipulations, T3SEs have evolved numerous novel folds that are compatible with some basic requirements: they should be able to easily unfold, pass through the narrow T3SS channel, and refold to an active form when on the other side. In this review, the various folds of T3SEs are presented with the emphasis placed on the functional and structural importance of α-helices and helical domains.
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Affiliation(s)
- Anastasia D. Gazi
- Unit of Technology & Service Ultrastructural Bio-Imaging (UTechS UBI), Institut Pasteur, 75015 Paris, France
- Correspondence: (A.D.G.); (V.E.F.)
| | - Michael Kokkinidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Nikolaou Plastira 100, Heraklion, 70013 Crete, Greece;
- Department of Biology, Voutes University Campus, University of Crete, Heraklion, 70013 Crete, Greece
| | - Vasiliki E. Fadouloglou
- Department of Molecular Biology & Genetics, Democritus University of Thrace, 68100 Alexandroupolis, Greece
- Correspondence: (A.D.G.); (V.E.F.)
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12
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Plesia M, Stevens OA, Lloyd GR, Kendall CA, Coldicott I, Kennerley AJ, Miller G, Shaw PJ, Mead RJ, Day JCC, Alix JJP. In Vivo Fiber Optic Raman Spectroscopy of Muscle in Preclinical Models of Amyotrophic Lateral Sclerosis and Duchenne Muscular Dystrophy. ACS Chem Neurosci 2021; 12:1768-1776. [PMID: 33950665 PMCID: PMC8154326 DOI: 10.1021/acschemneuro.0c00794] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 04/30/2021] [Indexed: 12/13/2022] Open
Abstract
Neuromuscular diseases result in muscle weakness, disability, and, in many instances, death. Preclinical models form the bedrock of research into these disorders, and the development of in vivo and potentially translational biomarkers for the accurate identification of disease is crucial. Spontaneous Raman spectroscopy can provide a rapid, label-free, and highly specific molecular fingerprint of tissue, making it an attractive potential biomarker. In this study, we have developed and tested an in vivo intramuscular fiber optic Raman technique in two mouse models of devastating human neuromuscular diseases, amyotrophic lateral sclerosis, and Duchenne muscular dystrophy (SOD1G93A and mdx, respectively). The method identified diseased and healthy muscle with high classification accuracies (area under the receiver operating characteristic curves (AUROC): 0.76-0.92). In addition, changes in diseased muscle over time were also identified (AUROCs 0.89-0.97). Key spectral changes related to proteins and the loss of α-helix protein structure. Importantly, in vivo recording did not cause functional motor impairment and only a limited, resolving tissue injury was seen on high-resolution magnetic resonance imaging. Lastly, we demonstrate that ex vivo muscle from human patients with these conditions produced similar spectra to those observed in mice. We conclude that spontaneous Raman spectroscopy of muscle shows promise as a translational research tool.
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Affiliation(s)
- Maria Plesia
- Sheffield
Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
| | - Oliver A. Stevens
- Interface
Analysis Centre, School of Physics, University
of Bristol, Bristol BS8 1TL, UK
| | - Gavin R. Lloyd
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, UK
- Biophotonics
Research Unit, Gloucestershire Hospitals
NHS Foundation Trust, Gloucester GL1 3NN, UK
| | - Catherine A. Kendall
- Biophotonics
Research Unit, Gloucestershire Hospitals
NHS Foundation Trust, Gloucester GL1 3NN, UK
| | - Ian Coldicott
- Sheffield
Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
| | | | - Gaynor Miller
- Department
of Oncology and Metabolism, University of
Sheffield, Sheffield S10 2RX, UK
| | - Pamela J. Shaw
- Sheffield
Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
- Cross-Faculty
Neuroscience Institute, University of Sheffield, Sheffield S10 2HQ, UK
| | - Richard J. Mead
- Sheffield
Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
- Cross-Faculty
Neuroscience Institute, University of Sheffield, Sheffield S10 2HQ, UK
| | - John C. C. Day
- Interface
Analysis Centre, School of Physics, University
of Bristol, Bristol BS8 1TL, UK
| | - James J. P. Alix
- Sheffield
Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK
- Cross-Faculty
Neuroscience Institute, University of Sheffield, Sheffield S10 2HQ, UK
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13
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Devaux F, Li X, Sluysmans D, Maurizot V, Bakalis E, Zerbetto F, Huc I, Duwez AS. Single-molecule mechanics of synthetic aromatic amide helices: Ultrafast and robust non-dissipative winding. Chem 2021. [DOI: 10.1016/j.chempr.2021.02.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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14
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Li Y, Hessel AL, Unger A, Ing D, Recker J, Koser F, Freundt JK, Linke WA. Graded titin cleavage progressively reduces tension and uncovers the source of A-band stability in contracting muscle. eLife 2020; 9:64107. [PMID: 33357376 PMCID: PMC7781594 DOI: 10.7554/elife.64107] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 12/23/2020] [Indexed: 12/11/2022] Open
Abstract
The giant muscle protein titin is a major contributor to passive force; however, its role in active force generation is unresolved. Here, we use a novel titin-cleavage (TC) mouse model that allows specific and rapid cutting of elastic titin to quantify how titin-based forces define myocyte ultrastructure and mechanics. We show that under mechanical strain, as TC doubles from heterozygous to homozygous TC muscles, Z-disks become increasingly out of register while passive and active forces are reduced. Interactions of elastic titin with sarcomeric actin filaments are revealed. Strikingly, when titin-cleaved muscles contract, myosin-containing A-bands become split and adjacent myosin filaments move in opposite directions while also shedding myosins. This establishes intact titin filaments as critical force-transmission networks, buffering the forces observed by myosin filaments during contraction. To perform this function, elastic titin must change stiffness or extensible length, unveiling its fundamental role as an activation-dependent spring in contracting muscle.
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Affiliation(s)
- Yong Li
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Anthony L Hessel
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Andreas Unger
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - David Ing
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Jannik Recker
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Franziska Koser
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Johanna K Freundt
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster, Muenster, Germany
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15
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Bergues-Pupo AE, Lipowsky R, Vila Verde A. Unfolding mechanism and free energy landscape of single, stable, alpha helices at low pull speeds. SOFT MATTER 2020; 16:9917-9928. [PMID: 33030193 DOI: 10.1039/d0sm01166e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Single alpha helices (SAHs) stable in isolated form are often found in motor proteins where they bridge functional domains. Understanding the mechanical response of SAHs is thus critical to understand their function. The quasi-static force-extension relation of a small number of SAHs is known from single-molecule experiments. Unknown, or still controversial, are the molecular scale details behind those observations. We show that the deformation mechanism of SAHs pulled from the termini at pull speeds approaching the quasi-static limit differs from that of typical helices found in proteins, which are stable only when interacting with other protein domains. Using molecular dynamics simulations with atomistic resolution at low pull speeds previously inaccessible to simulation, we show that SAHs start unfolding from the termini at all pull speeds we investigated. Unfolding proceeds residue-by-residue and hydrogen bond breaking is not the main event determining the barrier to unfolding. We use the molecular simulation data to test the cooperative sticky chain model. This model yields excellent fits of the force-extension curves and quantifies the distance, xE = 0.13 nm, to the transition state, the natural frequency of bond vibration, ν0 = 0.82 ns-1, and the height, V0 = 2.9 kcal mol-1, of the free energy barrier associated with the deformation of single residues. Our results demonstrate that the sticky chain model could advantageously be used to analyze experimental force-extension curves of SAHs and other biopolymers.
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Affiliation(s)
- Ana Elisa Bergues-Pupo
- Max Planck Institute of Colloids and Interfaces, Department of Theory & Bio-Systems, Am Mühlenberg 1, 14476 Potsdam, Germany.
| | - Reinhard Lipowsky
- Max Planck Institute of Colloids and Interfaces, Department of Theory & Bio-Systems, Am Mühlenberg 1, 14476 Potsdam, Germany.
| | - Ana Vila Verde
- Max Planck Institute of Colloids and Interfaces, Department of Theory & Bio-Systems, Am Mühlenberg 1, 14476 Potsdam, Germany.
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16
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Wang H, Shen B, Song Y, Lee M, Zhang W. Nanomechanical Properties of a Supramolecular Helix Stabilized by Non-Covalent Interactions. Macromol Rapid Commun 2020; 41:e2000453. [PMID: 32902027 DOI: 10.1002/marc.202000453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 08/30/2020] [Indexed: 11/06/2022]
Abstract
Supramolecular helices have unique properties and many potential applications, such as chiral separation and asymmetric catalysis. Mechanical property (stability) of the supramolecular helix plays important roles in their functions. Due to the limitation of detection method, it is quite challenging to investigate nanomechanical properties of individual supramolecular helices stabilized by pure supramolecular interactions. Here atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS) is used to study the nanomechanical properties of a thermal-responsive supramolecular helix. The unwinding force plateau is observed in the force-extension curve, and the rupture force of the helix is dependent on the loading rate. In addition, the force-induced unwinding process is reversible and there is almost no energy dissipation in the process. Furthermore, the result of thermal shape-fluctuation analysis shows that the persistence length of the supramolecular helix is about 222 nm, which is much larger than helical structure formed by double-stranded DNA (dsDNA). However, because of its unique backbone structure, the supramolecular helix exhibits higher dynamic flexibility during force-induced deformation, since the persistence length determined from the stretching experiment is much smaller (1.1 nm).
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Affiliation(s)
- Huijie Wang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Bowen Shen
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Yu Song
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Myongsoo Lee
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Wenke Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
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17
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A Region of UNC-89 (Obscurin) Lying between Two Protein Kinase Domains Is a Highly Elastic Spring Required for Proper Sarcomere Organization. J Mol Biol 2020; 432:4799-4814. [PMID: 32645312 DOI: 10.1016/j.jmb.2020.06.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/07/2020] [Accepted: 06/25/2020] [Indexed: 12/17/2022]
Abstract
In Caenorhabditis elegans, unc-89 encodes a set of giant multi-domain proteins (up 8081 residues) localized to the M-lines of muscle sarcomeres and required for normal sarcomere organization and whole-animal locomotion. Multiple UNC-89 isoforms contain two protein kinase domains. There is conservation in arrangement of domains between UNC-89 and its two mammalian homologs, obscurin and SPEG: kinase, a non-domain region of 647-742 residues, Ig domain, Fn3 domain and a second kinase domain. In all three proteins, this non-domain "interkinase region" has low sequence complexity, has high proline content, and lacks predicted secondary structure. We report that a major portion of this interkinase (571 residues out of 647 residues) when examined by single molecule force spectroscopy in vitro displays the properties of a random coil and acts as an entropic spring. We used CRISPR/Cas9 to create nematodes carrying an in-frame deletion of the same 571-residue portion of the interkinase. These animals display severe disorganization of all portions of the sarcomere in body wall muscle. Super-resolution microscopy reveals extra, short-A-bands lying close to the outer muscle cell membrane and between normally spaced A-bands. Nematodes with this in-frame deletion show defective locomotion and muscle force generation. We designed our CRISPR-generatedin-frame deletion to contain an HA tag at the N terminus of the large UNC-89 isoforms. This HA tag results in normal organization of body wall muscle, but approximately half the normal levels of the giant UNC-89 isoforms, dis-organization of pharyngeal muscle, small body size, and reduced muscle force, likely due to poor nutritional uptake.
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18
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Yang B, Liu Z, Liu H, Nash MA. Next Generation Methods for Single-Molecule Force Spectroscopy on Polyproteins and Receptor-Ligand Complexes. Front Mol Biosci 2020; 7:85. [PMID: 32509800 PMCID: PMC7248566 DOI: 10.3389/fmolb.2020.00085] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/16/2020] [Indexed: 12/31/2022] Open
Abstract
Single-molecule force spectroscopy with the atomic force microscope provides molecular level insights into protein function, allowing researchers to reconstruct energy landscapes and understand functional mechanisms in biology. With steadily advancing methods, this technique has greatly accelerated our understanding of force transduction, mechanical deformation, and mechanostability within single- and multi-domain polyproteins, and receptor-ligand complexes. In this focused review, we summarize the state of the art in terms of methodology and highlight recent methodological improvements for AFM-SMFS experiments, including developments in surface chemistry, considerations for protein engineering, as well as theory and algorithms for data analysis. We hope that by condensing and disseminating these methods, they can assist the community in improving data yield, reliability, and throughput and thereby enhance the information that researchers can extract from such experiments. These leading edge methods for AFM-SMFS will serve as a groundwork for researchers cognizant of its current limitations who seek to improve the technique in the future for in-depth studies of molecular biomechanics.
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Affiliation(s)
- Byeongseon Yang
- Department of Chemistry, University of Basel, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Zhaowei Liu
- Department of Chemistry, University of Basel, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Haipei Liu
- Department of Chemistry, University of Basel, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Michael A. Nash
- Department of Chemistry, University of Basel, Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
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19
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Sluysmans D, Willet N, Thevenot J, Lecommandoux S, Duwez AS. Single-molecule mechanical unfolding experiments reveal a critical length for the formation of α-helices in peptides. NANOSCALE HORIZONS 2020; 5:671-678. [PMID: 32226978 DOI: 10.1039/d0nh00036a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
α-Helix is the most predominant secondary structure in proteins and supports many functions in biological machineries. The conformation of the helix is dictated by many factors such as its primary sequence, intramolecular interactions, or the effect of the close environment. Several computational studies have proposed that there is a critical maximum length for the formation of intact compact helical structures, supporting the fact that most intact α-helices in proteins are constituted of a small number of amino acids. To obtain a detailed picture on the formation of α-helices in peptides and their mechanical stability, we have synthesized a long homopolypeptide of about 90 amino acids, poly(γ-benzyl-l-glutamate), and investigated its mechanical behaviour by AFM-based single-molecule force spectroscopy. The characteristic plateaus observed in the force-extension curves reveal the unfolding of a series of small helices (from 1 to 4) of about 20 amino acid residues connected to each other, rather than a long helix of 90 residues. Our results suggest the formation of a tertiary structure made of short helices with kinks, instead of an intact compact helical structure for sequences of more than 20 amino acid residues. To our knowledge, this is the first experimental evidence supporting the concept of a helical critical length previously proposed by several computational studies.
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Affiliation(s)
- Damien Sluysmans
- Molecular Systems Research Unit, University of Liège, Sart-Tilman B6a, 4000 Liège, Belgium.
| | - Nicolas Willet
- Molecular Systems Research Unit, University of Liège, Sart-Tilman B6a, 4000 Liège, Belgium. and Univ. Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, F-33600, Pessac, France
| | - Julie Thevenot
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, F-33600, Pessac, France
| | | | - Anne-Sophie Duwez
- Molecular Systems Research Unit, University of Liège, Sart-Tilman B6a, 4000 Liège, Belgium.
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20
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Lange S, Pinotsis N, Agarkova I, Ehler E. The M-band: The underestimated part of the sarcomere. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2020; 1867:118440. [PMID: 30738787 PMCID: PMC7023976 DOI: 10.1016/j.bbamcr.2019.02.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/16/2019] [Accepted: 02/05/2019] [Indexed: 12/20/2022]
Abstract
The sarcomere is the basic unit of the myofibrils, which mediate skeletal and cardiac Muscle contraction. Two transverse structures, the Z-disc and the M-band, anchor the thin (actin and associated proteins) and thick (myosin and associated proteins) filaments to the elastic filament system composed of titin. A plethora of proteins are known to be integral or associated proteins of the Z-disc and its structural and signalling role in muscle is better understood, while the molecular constituents of the M-band and its function are less well defined. Evidence discussed here suggests that the M-band is important for managing force imbalances during active muscle contraction. Its molecular composition is fine-tuned, especially as far as the structural linkers encoded by members of the myomesin family are concerned and depends on the specific mechanical characteristics of each particular muscle fibre type. Muscle activity signals from the M-band to the nucleus and affects transcription of sarcomeric genes, especially via serum response factor (SRF). Due to its important role as shock absorber in contracting muscle, the M-band is also more and more recognised as a contributor to muscle disease.
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Affiliation(s)
- Stephan Lange
- Biomedical Research Facility 2, School of Medicine, University of California, San Diego, Medical Sciences Research Bldg, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA; University of Gothenburg, Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, Gothenburg, Sweden
| | - Nikos Pinotsis
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Irina Agarkova
- InSphero, Wagistrasse 27, CH-8952 Schlieren, Switzerland
| | - Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, UK; School of Cardiovascular Medicine and Sciences, British Heart Foundation Research Excellence Centre, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, UK.
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21
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Vos BE, Martinez-Torres C, Burla F, Weisel JW, Koenderink GH. Revealing the molecular origins of fibrin's elastomeric properties by in situ X-ray scattering. Acta Biomater 2020; 104:39-52. [PMID: 31923718 DOI: 10.1016/j.actbio.2020.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/02/2020] [Accepted: 01/02/2020] [Indexed: 01/01/2023]
Abstract
Fibrin is an elastomeric protein forming highly extensible fiber networks that provide the scaffold of blood clots. Here we reveal the molecular mechanisms that explain the large extensibility of fibrin networks by performing in situ small angle X-ray scattering measurements while applying a shear deformation. We simultaneously measure shear-induced alignment of the fibers and changes in their axially ordered molecular packing structure. We show that fibrin networks exhibit distinct structural responses that set in consecutively as the shear strain is increased. They exhibit an entropic response at small strains (<5%), followed by progressive fiber alignment (>25% strain) and finally changes in the fiber packing structure at high strain (>100%). Stretching reduces the fiber packing order and slightly increases the axial periodicity, indicative of molecular unfolding. However, the axial periodicity changes only by 0.7%, much less than the 80% length increase of the fibers, suggesting that fiber elongation mainly stems from uncoiling of the natively disordered αC-peptide linkers that laterally bond the molecules. Upon removal of the load, the network structure returns to the original isotropic state, but the fiber structure becomes more ordered and adopts a smaller packing periodicity compared to the original state. We conclude that the hierarchical packing structure of fibrin fibers, with built-in disorder, makes the fibers extensible and allows for mechanical annealing. Our results provide a basis for interpreting the molecular basis of haemostatic and thrombotic disorders associated with clotting and provide inspiration to design resilient bio-mimicking materials. STATEMENT OF SIGNIFICANCE: Fibrin provides structural integrity to blood clots and is also widely used as a scaffold for tissue engineering. To fulfill their biological functions, fibrin networks have to be simultaneously compliant like skin and resilient against rupture. Here, we unravel the structural origin underlying this remarkable mechanical behaviour. To this end, we performed in situ measurements of fibrin structure across multiple length scales by combining X-ray scattering with shear rheology. Our findings show that fibrin sustains large strains by undergoing a sequence of structural changes on different scales with increasing strain levels. This demonstrates new mechanistic aspects of an important biomaterial's structure and its mechanical function, and serves as an example in the design of biomimicking materials.
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22
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Cai W, Zhang J, de Lange WJ, Gregorich ZR, Karp H, Farrell ET, Mitchell SD, Tucholski T, Lin Z, Biermann M, McIlwain SJ, Ralphe JC, Kamp TJ, Ge Y. An Unbiased Proteomics Method to Assess the Maturation of Human Pluripotent Stem Cell-Derived Cardiomyocytes. Circ Res 2019; 125:936-953. [PMID: 31573406 DOI: 10.1161/circresaha.119.315305] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
RATIONALE Human pluripotent stem cell (hPSC)-derived cardiomyocytes exhibit the properties of fetal cardiomyocytes, which limits their applications. Various methods have been used to promote maturation of hPSC-cardiomyocytes; however, there is a lack of an unbiased and comprehensive method for accurate assessment of the maturity of hPSC-cardiomyocytes. OBJECTIVE We aim to develop an unbiased proteomics strategy integrating high-throughput top-down targeted proteomics and bottom-up global proteomics for the accurate and comprehensive assessment of hPSC-cardiomyocyte maturation. METHODS AND RESULTS Utilizing hPSC-cardiomyocytes from early- and late-stage 2-dimensional monolayer culture and 3-dimensional engineered cardiac tissue, we demonstrated the high reproducibility and reliability of a top-down proteomics method, which enabled simultaneous quantification of contractile protein isoform expression and associated post-translational modifications. This method allowed for the detection of known maturation-associated contractile protein alterations and, for the first time, identified contractile protein post-translational modifications as promising new markers of hPSC-cardiomyocytes maturation. Most notably, decreased phosphorylation of α-tropomyosin was found to be associated with hPSC-cardiomyocyte maturation. By employing a bottom-up global proteomics strategy, we identified candidate maturation-associated markers important for sarcomere organization, cardiac excitability, and Ca2+ homeostasis. In particular, upregulation of myomesin 1 and transmembrane 65 was associated with hPSC-cardiomyocyte maturation and validated in cardiac development, making these promising markers for assessing maturity of hPSC-cardiomyocytes. We have further validated α-actinin isoforms, phospholamban, dystrophin, αB-crystallin, and calsequestrin 2 as novel maturation-associated markers, in the developing mouse cardiac ventricles. CONCLUSIONS We established an unbiased proteomics method that can provide accurate and specific assessment of the maturity of hPSC-cardiomyocytes and identified new markers of maturation. Furthermore, this integrated proteomics strategy laid a strong foundation for uncovering the molecular pathways involved in cardiac development and disease using hPSC-cardiomyocytes.
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Affiliation(s)
- Wenxuan Cai
- From the Molecular and Cellular Pharmacology Training Program (W.C., S.D.M., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison
| | - Jianhua Zhang
- Department of Medicine (J.Z., Z.R.G., M.B., T.J.K.), University of Wisconsin-Madison
| | - Willem J de Lange
- Department of Pediatrics (W.J.d.L., E.T.F., J.C.R.), University of Wisconsin-Madison
| | - Zachery R Gregorich
- Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Medicine (J.Z., Z.R.G., M.B., T.J.K.), University of Wisconsin-Madison
| | - Hannah Karp
- Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison
| | - Emily T Farrell
- Department of Pediatrics (W.J.d.L., E.T.F., J.C.R.), University of Wisconsin-Madison
| | - Stanford D Mitchell
- From the Molecular and Cellular Pharmacology Training Program (W.C., S.D.M., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison
| | - Trisha Tucholski
- From the Molecular and Cellular Pharmacology Training Program (W.C., S.D.M., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Chemistry (T.T., Y.G.), University of Wisconsin-Madison.,Department of Biostatistics and Medical Informatics (T.T., S.J.M.), University of Wisconsin-Madison
| | - Ziqing Lin
- Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison.,Human Proteomics Program (Z.L., Y.G.), University of Wisconsin-Madison
| | - Mitch Biermann
- Department of Medicine (J.Z., Z.R.G., M.B., T.J.K.), University of Wisconsin-Madison
| | - Sean J McIlwain
- Department of Biostatistics and Medical Informatics (T.T., S.J.M.), University of Wisconsin-Madison.,UW Carbone Cancer Center (S.J.M.), University of Wisconsin-Madison
| | - J Carter Ralphe
- Department of Pediatrics (W.J.d.L., E.T.F., J.C.R.), University of Wisconsin-Madison
| | - Timothy J Kamp
- From the Molecular and Cellular Pharmacology Training Program (W.C., S.D.M., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Medicine (J.Z., Z.R.G., M.B., T.J.K.), University of Wisconsin-Madison
| | - Ying Ge
- From the Molecular and Cellular Pharmacology Training Program (W.C., S.D.M., T.J.K., Y.G.), University of Wisconsin-Madison.,Department of Cell and Regenerative Biology (W.C., Z.R.G., H.K., S.D.M., Z.L., T.J.K., Y.G.), University of Wisconsin-Madison.,Human Proteomics Program (Z.L., Y.G.), University of Wisconsin-Madison.,Department of Chemistry (T.T., Y.G.), University of Wisconsin-Madison
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24
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Goktas M, Luo C, Sullan RMA, Bergues-Pupo AE, Lipowsky R, Vila Verde A, Blank KG. Molecular mechanics of coiled coils loaded in the shear geometry. Chem Sci 2018; 9:4610-4621. [PMID: 29899954 PMCID: PMC5969510 DOI: 10.1039/c8sc01037d] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 04/19/2018] [Indexed: 01/25/2023] Open
Abstract
Coiled coils are important nanomechanical building blocks in biological and biomimetic materials. A mechanistic molecular understanding of their structural response to mechanical load is essential for elucidating their role in tissues and for utilizing and tuning these building blocks in materials applications. Using a combination of single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations, we have investigated the mechanics of synthetic heterodimeric coiled coils of different length (3-4 heptads) when loaded in shear geometry. Upon shearing, we observe an initial rise in the force, which is followed by a constant force plateau and ultimately strand separation. The force required for strand separation depends on the coiled coil length and the applied loading rate, suggesting that coiled coil shearing occurs out of equilibrium. This out-of-equilibrium behaviour is determined by a complex structural response which involves helix uncoiling, uncoiling-assisted sliding of the helices relative to each other in the direction of the applied force as well as uncoiling-assisted dissociation perpendicular to the force axis. These processes follow a hierarchy of timescales with helix uncoiling being faster than sliding and sliding being faster than dissociation. In SMFS experiments, strand separation is dominated by uncoiling-assisted dissociation and occurs at forces between 25-45 pN for the shortest 3-heptad coiled coil and between 35-50 pN for the longest 4-heptad coiled coil. These values are highly similar to the forces required for shearing apart short double-stranded DNA oligonucleotides, reinforcing the potential role of coiled coils as nanomechanical building blocks in applications where protein-based structures are desired.
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Affiliation(s)
- Melis Goktas
- Max Planck Institute of Colloids and Interfaces , Mechano(bio)chemistry , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Chuanfu Luo
- Max Planck Institute of Colloids and Interfaces , Department of Theory & Bio-Systems , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Ruby May A Sullan
- Max Planck Institute of Colloids and Interfaces , Mechano(bio)chemistry , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Ana E Bergues-Pupo
- Max Planck Institute of Colloids and Interfaces , Department of Theory & Bio-Systems , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Reinhard Lipowsky
- Max Planck Institute of Colloids and Interfaces , Department of Theory & Bio-Systems , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Ana Vila Verde
- Max Planck Institute of Colloids and Interfaces , Department of Theory & Bio-Systems , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
| | - Kerstin G Blank
- Max Planck Institute of Colloids and Interfaces , Mechano(bio)chemistry , Science Park Potsdam-Golm , 14424 Potsdam , Germany .
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25
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Wang L, Geist J, Grogan A, Hu LYR, Kontrogianni-Konstantopoulos A. Thick Filament Protein Network, Functions, and Disease Association. Compr Physiol 2018; 8:631-709. [PMID: 29687901 PMCID: PMC6404781 DOI: 10.1002/cphy.c170023] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sarcomeres consist of highly ordered arrays of thick myosin and thin actin filaments along with accessory proteins. Thick filaments occupy the center of sarcomeres where they partially overlap with thin filaments. The sliding of thick filaments past thin filaments is a highly regulated process that occurs in an ATP-dependent manner driving muscle contraction. In addition to myosin that makes up the backbone of the thick filament, four other proteins which are intimately bound to the thick filament, myosin binding protein-C, titin, myomesin, and obscurin play important structural and regulatory roles. Consistent with this, mutations in the respective genes have been associated with idiopathic and congenital forms of skeletal and cardiac myopathies. In this review, we aim to summarize our current knowledge on the molecular structure, subcellular localization, interacting partners, function, modulation via posttranslational modifications, and disease involvement of these five major proteins that comprise the thick filament of striated muscle cells. © 2018 American Physiological Society. Compr Physiol 8:631-709, 2018.
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Affiliation(s)
- Li Wang
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Janelle Geist
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Li-Yen R. Hu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
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Batchelor M, Wolny M, Kurzawa M, Dougan L, Knight PJ, Peckham M. Determining Stable Single Alpha Helical (SAH) Domain Properties by Circular Dichroism and Atomic Force Microscopy. Methods Mol Biol 2018; 1805:185-211. [PMID: 29971719 DOI: 10.1007/978-1-4939-8556-2_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Stable, single α-helical (SAH) domains exist in a number of unconventional myosin isoforms, as well as other proteins. These domains are formed from sequences rich in charged residues (Arg, Lys, and Glu), they can be hundreds of residues long, and in isolation they can tolerate significant changes in pH and salt concentration without loss in helicity. Here we describe methods for the preparation and purification of SAH domains and SAH domain-containing constructs, using the myosin 10 SAH domain as an example. We go on to describe the use of circular dichroism spectroscopy and force spectroscopy with the atomic force microscope for the elucidation of structural and mechanical properties of these unusual helical species.
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Affiliation(s)
- Matthew Batchelor
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Marcin Wolny
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Marta Kurzawa
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Lorna Dougan
- Astbury Centre for Structural Molecular Biology and School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - Peter J Knight
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Michelle Peckham
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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Pernigo S, Fukuzawa A, Beedle AEM, Holt M, Round A, Pandini A, Garcia-Manyes S, Gautel M, Steiner RA. Binding of Myomesin to Obscurin-Like-1 at the Muscle M-Band Provides a Strategy for Isoform-Specific Mechanical Protection. Structure 2016; 25:107-120. [PMID: 27989621 PMCID: PMC5222588 DOI: 10.1016/j.str.2016.11.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/16/2016] [Accepted: 11/18/2016] [Indexed: 12/03/2022]
Abstract
The sarcomeric cytoskeleton is a network of modular proteins that integrate mechanical and signaling roles. Obscurin, or its homolog obscurin-like-1, bridges the giant ruler titin and the myosin crosslinker myomesin at the M-band. Yet, the molecular mechanisms underlying the physical obscurin(-like-1):myomesin connection, important for mechanical integrity of the M-band, remained elusive. Here, using a combination of structural, cellular, and single-molecule force spectroscopy techniques, we decode the architectural and functional determinants defining the obscurin(-like-1):myomesin complex. The crystal structure reveals a trans-complementation mechanism whereby an incomplete immunoglobulin-like domain assimilates an isoform-specific myomesin interdomain sequence. Crucially, this unconventional architecture provides mechanical stability up to forces of ∼135 pN. A cellular competition assay in neonatal rat cardiomyocytes validates the complex and provides the rationale for the isoform specificity of the interaction. Altogether, our results reveal a novel binding strategy in sarcomere assembly, which might have implications on muscle nanomechanics and overall M-band organization. The structure of the human obscurin-like-1:myomesin complex has been determined A myomesin sequence complements an immunoglobulin fold of obscurin-like-1 This binding mechanism provides mechanical stability up to forces of ∼135 pN Possible implications on muscle nanomechanics and M-band organization are discussed
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Affiliation(s)
- Stefano Pernigo
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Atsushi Fukuzawa
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Cardiovascular Division, King's College London BHF Centre of Research Excellence, London SE1 1UL, UK
| | - Amy E M Beedle
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Department of Physics, King's College London, London WC2R 2LS, UK
| | - Mark Holt
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Cardiovascular Division, King's College London BHF Centre of Research Excellence, London SE1 1UL, UK
| | - Adam Round
- European Molecular Biology Laboratory, Grenoble Outstation, 38042 Grenoble, France; School of Chemical and Physical Sciences, Keele University, Keele, Staffordshire, UK
| | - Alessandro Pandini
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Department of Computer Science and Synthetic Biology Theme, Brunel University London, London UB8 3PH, UK
| | - Sergi Garcia-Manyes
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Department of Physics, King's College London, London WC2R 2LS, UK.
| | - Mathias Gautel
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK; Cardiovascular Division, King's College London BHF Centre of Research Excellence, London SE1 1UL, UK.
| | - Roberto A Steiner
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK.
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28
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Vera AM, Carrión-Vázquez M. Direct Identification of Protein-Protein Interactions by Single-Molecule Force Spectroscopy. Angew Chem Int Ed Engl 2016; 55:13970-13973. [PMID: 27735106 DOI: 10.1002/anie.201605284] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 07/07/2016] [Indexed: 11/08/2022]
Abstract
Single-molecule force spectroscopy based on atomic force microscopy (AFM-SMFS) has allowed the measurement of the intermolecular forces involved in protein-protein interactions at the molecular level. While intramolecular interactions are routinely identified directly by the use of polyprotein fingerprinting, there is a lack of a general method to directly identify single-molecule intermolecular unbinding events. Here, we have developed an internally controlled strategy to measure protein-protein interactions by AFM-SMFS that allows the direct identification of dissociation force peaks while ensuring single-molecule conditions. Single-molecule identification is assured by polyprotein fingerprinting while the intermolecular interaction is reported by a characteristic increase in contour length released after bond rupture. The latter is due to the exposure to force of a third protein that covalently connects the interacting pair. We demonstrate this strategy with a cohesin-dockerin interaction.
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Affiliation(s)
- Andrés M Vera
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, Avda. Doctor Arce 37, E-, 28002, Madrid, Spain.
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), E-, 28049, Cantoblanco, Madrid, Spain.
| | - Mariano Carrión-Vázquez
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, Avda. Doctor Arce 37, E-, 28002, Madrid, Spain.
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), E-, 28049, Cantoblanco, Madrid, Spain.
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29
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Vera AM, Carrión-Vázquez M. Direct Identification of Protein-Protein Interactions by Single-Molecule Force Spectroscopy. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201605284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Andrés M. Vera
- Instituto Cajal; Consejo Superior de Investigaciones Científicas; Avda. Doctor Arce 37, E- 28002 Madrid Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), E-; 28049 Cantoblanco Madrid Spain
| | - Mariano Carrión-Vázquez
- Instituto Cajal; Consejo Superior de Investigaciones Científicas; Avda. Doctor Arce 37, E- 28002 Madrid Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), E-; 28049 Cantoblanco Madrid Spain
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30
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Gautel M, Djinović-Carugo K. The sarcomeric cytoskeleton: from molecules to motion. ACTA ACUST UNITED AC 2016; 219:135-45. [PMID: 26792323 DOI: 10.1242/jeb.124941] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Highly ordered organisation of striated muscle is the prerequisite for the fast and unidirectional development of force and motion during heart and skeletal muscle contraction. A group of proteins, summarised as the sarcomeric cytoskeleton, is essential for the ordered assembly of actin and myosin filaments into sarcomeres, by combining architectural, mechanical and signalling functions. This review discusses recent cell biological, biophysical and structural insight into the regulated assembly of sarcomeric cytoskeleton proteins and their roles in dissipating mechanical forces in order to maintain sarcomere integrity during passive extension and active contraction. α-Actinin crosslinks in the Z-disk show a pivot-and-rod structure that anchors both titin and actin filaments. In contrast, the myosin crosslinks formed by myomesin in the M-band are of a ball-and-spring type and may be crucial in providing stable yet elastic connections during active contractions, especially eccentric exercise.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics, and Cardiovascular Division, New Hunt's House, London SE1 1UL, UK
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, Vienna A-1030, Austria Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, Ljubljana 1000, Slovenia
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31
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Zhou T, Fleming JR, Franke B, Bogomolovas J, Barsukov I, Rigden DJ, Labeit S, Mayans O. CARP interacts with titin at a unique helical N2A sequence and at the domain Ig81 to form a structured complex. FEBS Lett 2016; 590:3098-110. [PMID: 27531639 DOI: 10.1002/1873-3468.12362] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/29/2016] [Accepted: 08/09/2016] [Indexed: 11/07/2022]
Abstract
The cardiac ankyrin repeat protein (CARP) is up-regulated in the myocardium during cardiovascular disease and in response to mechanical or toxic stress. Stress-induced CARP interacts with the N2A spring region of the titin filament to modulate muscle compliance. We characterize the interaction between CARP and titin-N2A and show that the binding site in titin spans the dual domain UN2A-Ig81. We find that the unique sequence UN2A is not structurally disordered, but that it has a stable, elongated α-helical fold that possibly acts as a constant force spring. Our findings portray CARP/titin-N2A as a structured node and help to rationalize the molecular basis of CARP mechanosensing in the sarcomeric I-band.
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Affiliation(s)
- Tiankun Zhou
- Department of Biology, University of Konstanz, Germany.,Institute of Integrative Biology, University of Liverpool, UK
| | - Jennifer R Fleming
- Department of Biology, University of Konstanz, Germany.,Institute of Integrative Biology, University of Liverpool, UK
| | | | - Julius Bogomolovas
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Igor Barsukov
- Institute of Integrative Biology, University of Liverpool, UK
| | - Daniel J Rigden
- Institute of Integrative Biology, University of Liverpool, UK
| | - Siegfried Labeit
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Olga Mayans
- Department of Biology, University of Konstanz, Germany. .,Institute of Integrative Biology, University of Liverpool, UK.
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32
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Hughes ML, Dougan L. The physics of pulling polyproteins: a review of single molecule force spectroscopy using the AFM to study protein unfolding. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:076601. [PMID: 27309041 DOI: 10.1088/0034-4885/79/7/076601] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
One of the most exciting developments in the field of biological physics in recent years is the ability to manipulate single molecules and probe their properties and function. Since its emergence over two decades ago, single molecule force spectroscopy has become a powerful tool to explore the response of biological molecules, including proteins, DNA, RNA and their complexes, to the application of an applied force. The force versus extension response of molecules can provide valuable insight into its mechanical stability, as well as details of the underlying energy landscape. In this review we will introduce the technique of single molecule force spectroscopy using the atomic force microscope (AFM), with particular focus on its application to study proteins. We will review the models which have been developed and employed to extract information from single molecule force spectroscopy experiments. Finally, we will end with a discussion of future directions in this field.
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Affiliation(s)
- Megan L Hughes
- School of Physics and Astronomy, University of Leeds, LS2 9JT, UK. Astbury Centre for Structural and Molecular Biology, University of Leeds, LS2 9JT, UK
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33
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Tych KM, Batchelor M, Hoffmann T, Wilson MC, Paci E, Brockwell DJ, Dougan L. Tuning protein mechanics through an ionic cluster graft from an extremophilic protein. SOFT MATTER 2016; 12:2688-2699. [PMID: 26809452 DOI: 10.1039/c5sm02938d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Proteins from extremophilic organisms provide excellent model systems to determine the role of non-covalent interactions in defining protein stability and dynamics as well as being attractive targets for the development of robust biomaterials. Hyperthermophilic proteins have a prevalence of salt bridges, relative to their mesophilic homologues, which are thought to be important for enhanced thermal stability. However, the impact of salt bridges on the mechanical properties of proteins is far from understood. Here, a combination of protein engineering, biophysical characterisation, single molecule force spectroscopy (SMFS) and molecular dynamics (MD) simulations directly investigates the role of salt bridges in the mechanical stability of two cold shock proteins; BsCSP from the mesophilic organism Bacillus subtilis and TmCSP from the hyperthermophilic organism Thermotoga maritima. Single molecule force spectroscopy shows that at ambient temperatures TmCSP is mechanically stronger yet, counter-intuitively, its native state can withstand greater deformation before unfolding (i.e. it is mechanically soft) compared with BsCSP. MD simulations were used to identify the location and quantify the population of salt bridges, and reveal that TmCSP contains a larger number of highly occupied salt bridges than BsCSP. To test the hypothesis that salt-bridges endow these mechanical properties on the hyperthermophilic CSP, a charged triple mutant (CTM) variant of BsCSP was generated by grafting an ionic cluster from TmCSP into the BsCSP scaffold. As expected CTM is thermodynamically more stable and mechanically softer than BsCSP. We show that a grafted ionic cluster can increase the mechanical softness of a protein and speculate that it could provide a mechanical recovery mechanism and that it may be a design feature applicable to other proteins.
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Affiliation(s)
- Katarzyna M Tych
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
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34
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Hoffmann T, Tych KM, Crosskey T, Schiffrin B, Brockwell DJ, Dougan L. Rapid and Robust Polyprotein Production Facilitates Single-Molecule Mechanical Characterization of β-Barrel Assembly Machinery Polypeptide Transport Associated Domains. ACS NANO 2015; 9:8811-21. [PMID: 26284289 DOI: 10.1021/acsnano.5b01962] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Single-molecule force spectroscopy by atomic force microscopy exploits the use of multimeric protein constructs, namely, polyproteins, to decrease the impact of nonspecific interactions, to improve data accumulation, and to allow the accommodation of benchmarking reference domains within the construct. However, methods to generate such constructs are either time- and labor-intensive or lack control over the length or the domain sequence of the obtained construct. Here, we describe an approach that addresses both of these shortcomings that uses Gibson assembly (GA) to generate a defined recombinant polyprotein rapidly using linker sequences. To demonstrate the feasibility of this approach, we used GA to make a polyprotein composed of alternating domains of I27 and TmCsp, (I27-TmCsp)3-I27)(GA), and showed the mechanical fingerprint, mechanical strength, and pulling speed dependence are the same as an analogous polyprotein constructed using the classical approach. After this benchmarking, we exploited this approach to facilitiate the mechanical characterization of POTRA domain 2 of BamA from E. coli (EcPOTRA2) by assembling the polyprotein (I27-EcPOTRA2)3-I27(GA). We show that, as predicted from the α + β topology, EcPOTRA2 domains are mechanically robust over a wide range of pulling speeds. Furthermore, we identify a clear correlation between mechanical robustness and brittleness for a range of other α + β proteins that contain the structural feature of proximal terminal β-strands in parallel geometry. We thus demonstrate that the GA approach is a powerful tool, as it circumvents the usual time- and labor-intensive polyprotein production process and allows for rapid production of new constructs for single-molecule studies. As shown for EcPOTRA2, this approach allows the exploration of the mechanical properties of a greater number of proteins and their variants. This improves our understanding of the relationship between structure and mechanical strength, increasing our ability to design proteins with tailored mechanical properties.
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Affiliation(s)
- Toni Hoffmann
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
| | - Katarzyna M Tych
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
| | - Thomas Crosskey
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
| | - Bob Schiffrin
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
| | - David J Brockwell
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
| | - Lorna Dougan
- School of Physics and Astronomy, ‡Astbury Centre for Structural and Molecular Biology, and §School of Molecular and Cellular Biology, University of Leeds , Leeds, LS2 9JT, U.K
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35
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Xiao S, Gräter F. Molecular basis of the mechanical hierarchy in myomesin dimers for sarcomere integrity. Biophys J 2015; 107:965-73. [PMID: 25140432 PMCID: PMC4142248 DOI: 10.1016/j.bpj.2014.06.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 05/26/2014] [Accepted: 06/16/2014] [Indexed: 01/08/2023] Open
Abstract
Myomesin is one of the most important structural molecules constructing the M-band in the force-generating unit of striated muscle, and a critical structural maintainer of the sarcomere. Using molecular dynamics simulations, we here dissect the mechanical properties of the structurally known building blocks of myomesin, namely α-helices, immunoglobulin (Ig) domains, and the dimer interface at myomesin's 13th Ig domain, covering the mechanically important C-terminal part of the molecule. We find the interdomain α-helices to be stabilized by the hydrophobic interface formed between the N-terminal half of these helices and adjacent Ig domains, and, interestingly, to show a rapid unfolding and refolding equilibrium especially under low axial forces up to ∼ 15 pN. These results support and yield atomic details for the notion of recent atomic-force microscopy experiments, namely, that the unique helices inserted between Ig domains in myomesin function as elastomers and force buffers. Our results also explain how the C-terminal dimer of two myomesin molecules is mechanically outperforming the helices and Ig domains in myomesin and elsewhere, explaining former experimental findings. This study provides a fresh view onto how myomesin integrates elastic helices, rigid immunoglobulin domains, and an extraordinarily resistant dimer into a molecular structure, to feature a mechanical hierarchy that represents a firm and yet extensible molecular anchor to guard the stability of the sarcomere.
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Affiliation(s)
- Senbo Xiao
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany
| | - Frauke Gräter
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany; Chinese Academy of Sciences-Max-Planck-Society Partner Institute and Key Laboratory for Computational Biology, Shanghai, China; Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany.
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36
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Chen Y, Radford SE, Brockwell DJ. Force-induced remodelling of proteins and their complexes. Curr Opin Struct Biol 2015; 30:89-99. [PMID: 25710390 PMCID: PMC4499843 DOI: 10.1016/j.sbi.2015.02.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/29/2015] [Accepted: 02/02/2015] [Indexed: 11/23/2022]
Abstract
Force can drive conformational changes in proteins, as well as modulate their stability and the affinity of their complexes, allowing a mechanical input to be converted into a biochemical output. These properties have been utilised by nature and force is now recognised to be widely used at the cellular level. The effects of force on the biophysical properties of biological systems can be large and varied. As these effects are only apparent in the presence of force, studies on the same proteins using traditional ensemble biophysical methods can yield apparently conflicting results. Where appropriate, therefore, force measurements should be integrated with other experimental approaches to understand the physiological context of the system under study.
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Affiliation(s)
- Yun Chen
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
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37
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Benian GM, Mayans O. Titin and obscurin: giants holding hands and discovery of a new Ig domain subset. J Mol Biol 2014; 427:707-714. [PMID: 25555989 DOI: 10.1016/j.jmb.2014.12.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Guy M Benian
- Department of Pathology, Emory University, Atlanta, GA 30322, USA.
| | - Olga Mayans
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
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38
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Schoeler C, Malinowska KH, Bernardi RC, Milles LF, Jobst MA, Durner E, Ott W, Fried DB, Bayer EA, Schulten K, Gaub HE, Nash MA. Ultrastable cellulosome-adhesion complex tightens under load. Nat Commun 2014; 5:5635. [PMID: 25482395 PMCID: PMC4266597 DOI: 10.1038/ncomms6635] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 10/22/2014] [Indexed: 11/09/2022] Open
Abstract
Challenging environments have guided nature in the development of ultrastable protein complexes. Specialized bacteria produce discrete multi-component protein networks called cellulosomes to effectively digest lignocellulosic biomass. While network assembly is enabled by protein interactions with commonplace affinities, we show that certain cellulosomal ligand-receptor interactions exhibit extreme resistance to applied force. Here, we characterize the ligand-receptor complex responsible for substrate anchoring in the Ruminococcus flavefaciens cellulosome using single-molecule force spectroscopy and steered molecular dynamics simulations. The complex withstands forces of 600-750 pN, making it one of the strongest bimolecular interactions reported, equivalent to half the mechanical strength of a covalent bond. Our findings demonstrate force activation and inter-domain stabilization of the complex, and suggest that certain network components serve as mechanical effectors for maintaining network integrity. This detailed understanding of cellulosomal network components may help in the development of biocatalysts for production of fuels and chemicals from renewable plant-derived biomass.
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Affiliation(s)
- Constantin Schoeler
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Klara H Malinowska
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Rafael C Bernardi
- Theoretical and Computational Biophysics Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Lukas F Milles
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Markus A Jobst
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Ellis Durner
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Wolfgang Ott
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Daniel B Fried
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Klaus Schulten
- 1] Theoretical and Computational Biophysics Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA [2] Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Hermann E Gaub
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
| | - Michael A Nash
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany
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39
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Wolny M, Batchelor M, Knight PJ, Paci E, Dougan L, Peckham M. Stable single α-helices are constant force springs in proteins. J Biol Chem 2014; 289:27825-35. [PMID: 25122759 PMCID: PMC4183817 DOI: 10.1074/jbc.m114.585679] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Single α-helix (SAH) domains are rich in charged residues (Arg, Lys, and Glu) and stable in solution over a wide range of pH and salt concentrations. They are found in many different proteins where they bridge two functional domains. To test the idea that their high stability might enable these proteins to resist unfolding along their length, the properties and unfolding behavior of the predicted SAH domain from myosin-10 were characterized. The expressed and purified SAH domain was highly helical, melted non-cooperatively, and was monomeric as shown by circular dichroism and mass spectrometry as expected for a SAH domain. Single molecule force spectroscopy experiments showed that the SAH domain unfolded at very low forces (<30 pN) without a characteristic unfolding peak. Molecular dynamics simulations showed that the SAH domain unfolds progressively as the length is increased and refolds progressively as the length is reduced. This enables the SAH domain to act as a constant force spring in the mechanically dynamic environment of the cell.
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Affiliation(s)
- Marcin Wolny
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Matthew Batchelor
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Peter J Knight
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Emanuele Paci
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Lorna Dougan
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Michelle Peckham
- From the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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40
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Kreuzer SM, Moon TJ, Elber R. Catch bond-like kinetics of helix cracking: network analysis by molecular dynamics and milestoning. J Chem Phys 2013; 139:121902. [PMID: 24089714 PMCID: PMC3716791 DOI: 10.1063/1.4811366] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 05/29/2013] [Indexed: 12/29/2022] Open
Abstract
The first events of unfolding of secondary structure under load are considered with Molecular Dynamics simulations and Milestoning analysis of a long helix (126 amino acids). The Mean First Passage Time is a non-monotonic function of the applied load with a maximum of 3.6 ns at about 20 pN. Network analysis of the reaction space illustrates the opening and closing of an off-pathway trap that slows unfolding at intermediate load levels. It is illustrated that the nature of the reaction networks changes as a function of load, demonstrating that the process is far from one-dimensional.
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Affiliation(s)
- Steven M Kreuzer
- Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712, USA
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Bertz M, Buchner J, Rief M. Mechanical Stability of the Antibody Domain CH3 Homodimer in Different Oxidation States. J Am Chem Soc 2013; 135:15085-91. [DOI: 10.1021/ja405076j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Morten Bertz
- Physik Department
E22, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Johannes Buchner
- Chemie Department, Technische Universität München, Lichtenbergstraße 4, 85748 Garching, Germany
- Munich Center for Integrated Protein Science (CIPSM), 81377 München, Germany
| | - Matthias Rief
- Physik Department
E22, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
- Munich Center for Integrated Protein Science (CIPSM), 81377 München, Germany
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Affiliation(s)
- Korosh Torabi
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - George C. Schatz
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
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Hoffmann T, Tych KM, Hughes ML, Brockwell DJ, Dougan L. Towards design principles for determining the mechanical stability of proteins. Phys Chem Chem Phys 2013; 15:15767-80. [DOI: 10.1039/c3cp52142g] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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44
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Zoldák G, Rief M. Force as a single molecule probe of multidimensional protein energy landscapes. Curr Opin Struct Biol 2012; 23:48-57. [PMID: 23279960 DOI: 10.1016/j.sbi.2012.11.007] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/26/2012] [Accepted: 11/26/2012] [Indexed: 01/06/2023]
Abstract
Force spectroscopy has developed into an indispensable tool for studying folding and binding of proteins on a single molecule level in real time. Design of the pulling geometry allows tuning the reaction coordinate in a very precise manner. Many recent experiments have taken advantage of this possibility and have provided detailed insight the folding pathways on the complex high dimensional energy landscape. Beyond its potential to provide control over the reaction coordinate, force is also an important physiological parameter that affects protein conformation under in vivo conditions. Single molecule force spectroscopy studies have started to unravel the response and adaptation of force bearing protein structures to mechanical loads.
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Affiliation(s)
- Gabriel Zoldák
- Physik Department E22, Technische Universität München, James-Franck-Strasse, 85748 Garching, Germany
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45
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Superhelical architecture of the myosin filament-linking protein myomesin with unusual elastic properties. PLoS Biol 2012; 10:e1001261. [PMID: 22347812 PMCID: PMC3279516 DOI: 10.1371/journal.pbio.1001261] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 01/05/2012] [Indexed: 01/27/2023] Open
Abstract
The muscle M-band protein myomesin comprises a 36 nm long filament made of repetitive immunoglobulin–helix modules that can stretch to 2.5-fold this length, demonstrating substantial molecular elasticity. Active muscles generate substantial mechanical forces by the contraction/relaxation cycle, and, to maintain an ordered state, they require molecular structures of extraordinary stability. These forces are sensed and buffered by unusually long and elastic filament proteins with highly repetitive domain arrays. Members of the myomesin protein family function as molecular bridges that connect major filament systems in the central M-band of muscle sarcomeres, which is a central locus of passive stress sensing. To unravel the mechanism of molecular elasticity in such filament-connecting proteins, we have determined the overall architecture of the complete C-terminal immunoglobulin domain array of myomesin by X-ray crystallography, electron microscopy, solution X-ray scattering, and atomic force microscopy. Our data reveal a dimeric tail-to-tail filament structure of about 360 Å in length, which is folded into an irregular superhelical coil arrangement of almost identical α-helix/domain modules. The myomesin filament can be stretched to about 2.5-fold its original length by reversible unfolding of these linkers, a mechanism that to our knowledge has not been observed previously. Our data explain how myomesin could act as a highly elastic ribbon to maintain the overall structural organization of the sarcomeric M-band. In general terms, our data demonstrate how repetitive domain modules such as those found in myomesin could generate highly elastic protein structures in highly organized cell systems such as muscle sarcomeres. The contraction and relaxation cycles of active muscles generate substantial mechanical forces, both axially and radially, that place extraordinary stress on the molecular structures within the muscle fibers. These forces are sensed and buffered by unusually long and elastic filament proteins with highly repetitive domain structures. Myomesin is one such repetitive filament protein that is thought to form bridges between the main contractile filaments of the muscle, providing the muscle structure with resistance in the radial dimension. To investigate how the repetitive structure of myomesin contributes to muscle elasticity, we determined the overall architecture of its complete repetitive domain array using a combination of four complementary structural biology methods. Our study reveals a long, dimeric tail-to-tail filament structure folded into an irregular superhelical coil arrangement of almost identical domain modules separated by short linkers. When we applied tension to these myomesin filaments, we found they could stretch to about 2.5 times their original length by unfolding these linkers, and then return to their original state when the tension was removed. Our findings explain how myomesin might adapt its overall length in response to the changing dimensions of the contracting and relaxing muscle, so acting as a highly elastic ribbon that maintains the overall structural organization of the muscle fibers. More generally, these findings demonstrate how repetitive domain modules, such as those in myomesin, can provide elasticity to highly organized biological structures.
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Abstract
The muscle M-band protein myomesin comprises a 36-nm long filament made of repetitive immunoglobulin–helix modules that can stretch to 2.5-fold this length, demonstrating substantial molecular elasticity. Skeletal and cardiac muscles are remarkable biological machines that support and move our bodies and power the rhythmic work of our lungs and hearts. As well as producing active contractile force, muscles are also passively elastic, which is essential to their performance. The origins of both active contractile and passive elastic forces can be traced to the individual proteins that make up the highly ordered structure of muscle. In this Primer, we describe the organization of sarcomeres—the structural units that produce contraction—and the nature of the proteins that make muscle elastic. In particular, we focus on an elastic protein called myomesin, whose novel modular architecture helps explain elasticity.
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Affiliation(s)
- Larissa Tskhovrebova
- Astbury Centre for Structural Molecular Biology and Institute for Molecular and Cellular Biology, Leeds University, Leeds, United Kingdom
| | - John Trinick
- Astbury Centre for Structural Molecular Biology and Institute for Molecular and Cellular Biology, Leeds University, Leeds, United Kingdom
- * E-mail:
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47
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Hoffmann T, Dougan L. Single molecule force spectroscopy using polyproteins. Chem Soc Rev 2012; 41:4781-96. [DOI: 10.1039/c2cs35033e] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Ponmurugan M, Vemparala S. Transient-state fluctuationlike relation for the driving force on a biomolecule. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:060101. [PMID: 22304027 DOI: 10.1103/physreve.84.060101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Indexed: 05/31/2023]
Abstract
In experiments and simulations the force acting on a single biomolecular system has been observed as a fluctuating quantity if the system is driven under constant velocity. We ask the question that is analogous to transient state entropy production and work fluctuation relations whether the force fluctuations observed in the single biomolecular system satisfy a transient state fluctuationlike relation, and the answer is in the affirmative. Using a constant velocity pulling steered molecular dynamics simulation study for protein unfolding, we confirm that the force fluctuations of this single biomolecular system satisfy a transient-state fluctuationlike relation 1/γ(T,v) ln[P(v)(+f)/P(v)(-f)] = f. P(v)(±f) is the probability of positive and negative values of forces f = f · for a given unfolding velocity of magnitude v and the pulling direction n, nis the unit vector of n, and γ(T,v) is a factor that depends on initial equilibrium temperature T and the unfolding velocity. For different unfolding velocities we find that the system in the nonequilibrium pulling region displays substantial negative fluctuation in its unfolding force when velocity decreases. A negative value of force may indicate the emergence of refolding behavior during protein unfolding. We also find that γ(T,v) ~ T(-δ)v(α) and the system relaxation time τ(T,v) ~ T(δ)v(-(1+α), where α and δ are scaling exponents.
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Affiliation(s)
- M Ponmurugan
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India.
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