1
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Monck C, Elani Y, Ceroni F. Genetically programmed synthetic cells for thermo-responsive protein synthesis and cargo release. Nat Chem Biol 2024; 20:1380-1386. [PMID: 38969863 PMCID: PMC11427347 DOI: 10.1038/s41589-024-01673-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 06/06/2024] [Indexed: 07/07/2024]
Abstract
Synthetic cells containing genetic programs and protein expression machinery are increasingly recognized as powerful counterparts to engineered living cells in the context of biotechnology, therapeutics and cellular modelling. So far, genetic regulation of synthetic cell activity has been largely confined to chemical stimuli; to unlock their potential in applied settings, engineering stimuli-responsive synthetic cells under genetic regulation is imperative. Here we report the development of temperature-sensitive synthetic cells that control protein production by exploiting heat-responsive mRNA elements. This is achieved by combining RNA thermometer technology, cell-free protein expression and vesicle-based synthetic cell design to create cell-sized capsules able to initiate synthesis of both soluble proteins and membrane proteins at defined temperatures. We show that the latter allows for temperature-controlled cargo release phenomena with potential implications for biomedicine. Platforms like the one presented here can pave the way for customizable, genetically programmed synthetic cells under thermal control to be used in biotechnology.
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Affiliation(s)
- Carolina Monck
- Department of Chemical Engineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, London, UK
- fabriCELL, Imperial College London, London, UK
| | - Yuval Elani
- Department of Chemical Engineering, Imperial College London, London, UK.
- Imperial College Centre for Synthetic Biology, London, UK.
- fabriCELL, Imperial College London, London, UK.
| | - Francesca Ceroni
- Department of Chemical Engineering, Imperial College London, London, UK.
- Imperial College Centre for Synthetic Biology, London, UK.
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2
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Okyay C, Dessaux D, Ramirez R, Mathé J, Basdevant N. Exploring ssDNA translocation through α-hemolysin using coarse-grained steered molecular dynamics. NANOSCALE 2024; 16:15677-15689. [PMID: 39078242 DOI: 10.1039/d4nr01581a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/31/2024]
Abstract
Protein nanopores have proven to be effective for single-molecule studies, particularly for single-stranded DNA (ssDNA) translocation. Previous experiments demonstrated their ability to distinguish differences in purine and pyrimidine bases and in the orientation of the ssDNA molecule inside nanopores. Unfortunately, the microscopic details of ssDNA translocation over experimental time scales, which are not accessible through all-atom molecular dynamics (MD), have yet to be examined. However, coarse-grained (CG) MD simulations enable systems to be simulated over longer characteristic times closer to experiments than all-atom MD. This paper studies ssDNA translocation through α-hemolysin nanopores exploiting steered MD using the MARTINI CG force field. The impacts of the sequence length, orientation inside the nanopore and DNA charges on translocation dynamics as well as the conformational dynamics of ssDNA during the translocation are explored. Our results highlight the efficacy of CG molecular dynamics in capturing the experimental properties of ssDNA translocation, including a wide distribution in translocation times per base. In particular, the phosphate charges of the DNA molecule are crucial in the translocation dynamics and impact the translocation rate. Additionally, the influence of the ssDNA molecule orientation on the translocation rate is explained by the conformational differences of ssDNA inside the nanopore during its translocation. Our study emphasizes the significance of obtaining sufficient statistics via CG MD, which can elucidate the great variety of translocation processes.
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Affiliation(s)
- Cagla Okyay
- Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, 91025, Évry-Courcouronnes, France.
| | - Delphine Dessaux
- Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, 91025, Évry-Courcouronnes, France.
| | - Rosa Ramirez
- Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, 91025, Évry-Courcouronnes, France.
| | - Jérôme Mathé
- Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, 91025, Évry-Courcouronnes, France.
| | - Nathalie Basdevant
- Université Paris-Saclay, Univ Evry, CY Cergy Paris Université, CNRS, LAMBE, 91025, Évry-Courcouronnes, France.
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3
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Si W, Zhang Z, Chen J, Wu G, Zhang Y, Sha J. Protein Deceleration and Sequencing Using Si 3N 4-CNT Hybrid Nanopores. Chemphyschem 2024; 25:e202300866. [PMID: 38267372 DOI: 10.1002/cphc.202300866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/24/2024] [Accepted: 01/24/2024] [Indexed: 01/26/2024]
Abstract
Protein sequencing is crucial for understanding the complex mechanisms driving biological functions and is of utmost importance in molecular diagnostics and medication development. Nanopores have become an effective tool for single molecule sensing, however, the weak charge and non-uniform charge distribution of protein make capturing and sensing very challenging, which poses a significant obstacle to the development of nanopore-based protein sequencing. In this study, to facilitate capturing of the unfolded protein, highly charged peptide was employed in our simulations, we found that the velocity of unfolded peptide translocating through a hybrid nanopore composed of silicon nitride membrane and carbon nanotube is much slower compared to bare silicon nitride nanopore, it is due to the significant interaction between amino acids and the surface of carbon nanotube. Moreover, by introducing variations in the charge states at the boundaries of carbon nanotube nanopores, the competition and combination of the electrophoretic and electroosmotic flows through the nanopores could be controlled, we then successfully regulated the translocation velocity of unfolded proteins through the hybrid nanopores. The proposed hybrid nanopore effectively retards the translocation velocity of protein through it, facilitates the acquisition of ample information for accurate amino acid identification.
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Affiliation(s)
- Wei Si
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, 211100, China
| | - Zhen Zhang
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, 211100, China
| | - Jiayi Chen
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, 211100, China
| | - Gensheng Wu
- School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing, 210037, China
| | - Yin Zhang
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, 211100, China
| | - Jingjie Sha
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, 211100, China
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4
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Shinn EJ, Tajkhorshid E. Generating Concentration Gradients across Membranes for Molecular Dynamics Simulations of Periodic Systems. Int J Mol Sci 2024; 25:3616. [PMID: 38612428 PMCID: PMC11012027 DOI: 10.3390/ijms25073616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 03/15/2024] [Accepted: 03/20/2024] [Indexed: 04/14/2024] Open
Abstract
The plasma membrane forms the boundary between a living entity and its environment and acts as a barrier to permeation and flow of substances. Several computational means of calculating permeability have been implemented for molecular dynamics (MD) simulations-based approaches. Except for double bilayer systems, most permeability studies have been performed under equilibrium conditions, in large part due to the challenges associated with creating concentration gradients in simulations utilizing periodic boundary conditions. To enhance the scientific understanding of permeation and complement the existing computational means of characterizing membrane permeability, we developed a non-equilibrium method that enables the generation and maintenance of steady-state gradients in MD simulations. We utilize PBCs advantageously by imposing a directional bias to the motion of permeants so that their crossing of the boundary replenishes the gradient, like a previous study on ions. Under these conditions, a net flow of permeants across membranes may be observed to determine bulk permeability by a direct application of J=PΔc. In the present study, we explore the results of its application to an exemplary O2 and POPC bilayer system, demonstrating accurate and precise permeability measurements. In addition, we illustrate the impact of permeant concentration and the choice of thermostat on the permeability. Moreover, we demonstrate that energetics of permeation can be closely examined by the dissipation of the gradient across the membrane to gain nuanced insights into the thermodynamics of permeability.
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Affiliation(s)
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Resource Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;
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5
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Hasdemir HS, Pozzi N, Tajkhorshid E. Atomistic Characterization of Beta-2-Glycoprotein I Domain V Interaction with Anionic Membranes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.19.585743. [PMID: 38562685 PMCID: PMC10983932 DOI: 10.1101/2024.03.19.585743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Background Interaction of beta-2-glycoprotein I ( β 2 GPI) with anionic membranes is crucial in antiphospholipid syndrome (APS), implicating the role of it's membrane bind-ing domain, Domain V (DV). The mechanism of DV binding to anionic lipids is not fully understood. Objectives This study aims to elucidate the mechanism by which DV of β 2 GPI binds to anionic membranes. Methods We utilized molecular dynamics (MD) simulations to investigate the struc-tural basis of anionic lipid recognition by DV. To corroborate the membrane-binding mode identified in the HMMM simulations, we conducted additional simulations using a full mem-brane model. Results The study identified critical regions in DV, namely the lysine-rich loop and the hydrophobic loop, essential for membrane association via electrostatic and hydrophobic interactions, respectively. A novel lysine pair contributing to membrane binding was also discovered, providing new insights into β 2 GPI's membrane interaction. Simulations revealed two distinct binding modes of DV to the membrane, with mode 1 characterized by the insertion of the hydrophobic loop into the lipid bilayer, suggesting a dominant mechanism for membrane association. This interaction is pivotal for the pathogenesis of APS, as it facilitates the recognition of β 2 GPI by antiphospholipid antibodies. Conclusion The study advances our understanding of the molecular interactions be-tween β 2 GPI's DV and anionic membranes, crucial for APS pathogenesis. It highlights the importance of specific regions in DV for membrane binding and reveals a predominant bind-ing mode. These findings have significant implications for APS diagnostics and therapeutics, offering a deeper insight into the molecular basis of the syndrome.
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6
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Coshic K, Maffeo C, Winogradoff D, Aksimentiev A. The structure and physical properties of a packaged bacteriophage particle. Nature 2024; 627:905-914. [PMID: 38448589 PMCID: PMC11196859 DOI: 10.1038/s41586-024-07150-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 02/01/2024] [Indexed: 03/08/2024]
Abstract
A string of nucleotides confined within a protein capsid contains all the instructions necessary to make a functional virus particle, a virion. Although the structure of the protein capsid is known for many virus species1,2, the three-dimensional organization of viral genomes has mostly eluded experimental probes3,4. Here we report all-atom structural models of an HK97 virion5, including its entire 39,732 base pair genome, obtained through multiresolution simulations. Mimicking the action of a packaging motor6, the genome was gradually loaded into the capsid. The structure of the packaged capsid was then refined through simulations of increasing resolution, which produced a 26 million atom model of the complete virion, including water and ions confined within the capsid. DNA packaging occurs through a loop extrusion mechanism7 that produces globally different configurations of the packaged genome and gives each viral particle individual traits. Multiple microsecond-long all-atom simulations characterized the effect of the packaged genome on capsid structure, internal pressure, electrostatics and diffusion of water, ions and DNA, and revealed the structural imprints of the capsid onto the genome. Our approach can be generalized to obtain complete all-atom structural models of other virus species, thereby potentially revealing new drug targets at the genome-capsid interface.
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Affiliation(s)
- Kush Coshic
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Christopher Maffeo
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - David Winogradoff
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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7
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Radka CD, Grace CR, Hasdemir HS, Li Y, Rodriguez CC, Rodrigues P, Oldham ML, Qayyum MZ, Pitre A, MacCain WJ, Kalathur RC, Tajkhorshid E, Rock CO. The carboxy terminus causes interfacial assembly of oleate hydratase on a membrane bilayer. J Biol Chem 2024; 300:105627. [PMID: 38211817 PMCID: PMC10847778 DOI: 10.1016/j.jbc.2024.105627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/13/2024] Open
Abstract
The soluble flavoprotein oleate hydratase (OhyA) hydrates the 9-cis double bond of unsaturated fatty acids. OhyA substrates are embedded in membrane bilayers; OhyA must remove the fatty acid from the bilayer and enclose it in the active site. Here, we show that the positively charged helix-turn-helix motif in the carboxy terminus (CTD) is responsible for interacting with the negatively charged phosphatidylglycerol (PG) bilayer. Super-resolution microscopy of Staphylococcus aureus cells expressing green fluorescent protein fused to OhyA or the CTD sequence shows subcellular localization along the cellular boundary, indicating OhyA is membrane-associated and the CTD sequence is sufficient for membrane recruitment. Using cryo-electron microscopy, we solved the OhyA dimer structure and conducted 3D variability analysis of the reconstructions to assess CTD flexibility. Our surface plasmon resonance experiments corroborated that OhyA binds the PG bilayer with nanomolar affinity and we found the CTD sequence has intrinsic PG binding properties. We determined that the nuclear magnetic resonance structure of a peptide containing the CTD sequence resembles the OhyA crystal structure. We observed intermolecular NOE from PG liposome protons next to the phosphate group to the CTD peptide. The addition of paramagnetic MnCl2 indicated the CTD peptide binds the PG surface but does not insert into the bilayer. Molecular dynamics simulations, supported by site-directed mutagenesis experiments, identify key residues in the helix-turn-helix that drive membrane association. The data show that the OhyA CTD binds the phosphate layer of the PG surface to obtain bilayer-embedded unsaturated fatty acids.
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Affiliation(s)
- Christopher D Radka
- Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, Kentucky, USA; Department of Host Microbe Interactions, St Jude Children's Research Hospital, Memphis, Tennessee, USA.
| | - Christy R Grace
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Hale S Hasdemir
- Theoretical and Computational Biophysics Group, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Yupeng Li
- Theoretical and Computational Biophysics Group, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Carlos C Rodriguez
- Theoretical and Computational Biophysics Group, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Patrick Rodrigues
- Hartwell Center of Biotechnology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Michael L Oldham
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - M Zuhaib Qayyum
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Aaron Pitre
- Cell and Tissue Imaging Center, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - William J MacCain
- Department of Host Microbe Interactions, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ravi C Kalathur
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Charles O Rock
- Department of Host Microbe Interactions, St Jude Children's Research Hospital, Memphis, Tennessee, USA
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8
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Tripathi P, Mehrafrooz B, Aksimentiev A, Jackson SE, Gruebele M, Wanunu M. A Marcus-Type Inverted Region in the Translocation Kinetics of a Knotted Protein. J Phys Chem Lett 2023; 14:10719-10726. [PMID: 38009629 PMCID: PMC11176711 DOI: 10.1021/acs.jpclett.3c02183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Knotted proteins are rare but important species, yet how their complex topologies affect their physical properties is not fully understood. Here we combine single molecule nanopore experiments and all-atom MD simulations to study the electric-field-driven unfolding during the translocation through a model pore of individual protein knots important for methylating tRNA. One of these knots shows an unusual behavior that resembles the behavior of electrons hopping between two potential surfaces: as the electric potential driving the translocation reaction is increased, the rate eventually plateaus or slows back down in the "Marcus inverted regime". Our results shed light on the influence of topology in knotted proteins on their forced translocation through a pore connecting two electrostatic potential wells.
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Affiliation(s)
- Prabhat Tripathi
- Department of Chemistry, Indian Institute of Technology (Banaras Hindu University), Varanasi, UP-221005, India
| | - Behzad Mehrafrooz
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL-61801, USA
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL-61801, USA
| | - Sophie E. Jackson
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield `Road, Cambridge CB2 1EW, UK
| | - Martin Gruebele
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL-61801, USA
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, MA-02115, USA
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9
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Tang Q, Sinclair M, Hasdemir HS, Stein RA, Karakas E, Tajkhorshid E, Mchaourab HS. Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter. Nat Commun 2023; 14:7184. [PMID: 37938578 PMCID: PMC10632425 DOI: 10.1038/s41467-023-42937-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/26/2023] [Indexed: 11/09/2023] Open
Abstract
Here we used cryo-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy (DEER), and molecular dynamics (MD) simulations, to capture and characterize ATP- and substrate-bound inward-facing (IF) and occluded (OC) conformational states of the heterodimeric ATP binding cassette (ABC) multidrug exporter BmrCD in lipid nanodiscs. Supported by DEER analysis, the structures reveal that ATP-powered isomerization entails changes in the relative symmetry of the BmrC and BmrD subunits that propagates from the transmembrane domain to the nucleotide binding domain. The structures uncover asymmetric substrate and Mg2+ binding which we hypothesize are required for triggering ATP hydrolysis preferentially in one of the nucleotide-binding sites. MD simulations demonstrate that multiple lipid molecules differentially bind the IF versus the OC conformation thus establishing that lipid interactions modulate BmrCD energy landscape. Our findings are framed in a model that highlights the role of asymmetric conformations in the ATP-coupled transport with general implications to the mechanism of ABC transporters.
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Affiliation(s)
- Qingyu Tang
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Matt Sinclair
- Theoretical and Computational Biophysics Group, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Hale S Hasdemir
- Theoretical and Computational Biophysics Group, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Erkan Karakas
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA.
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10
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Dehghani-Ghahnaviyeh S, Smith M, Xia Y, Dousis A, Grossfield A, Sur S. Ionizable Amino Lipids Distribution and Effects on DSPC/Cholesterol Membranes: Implications for Lipid Nanoparticle Structure. J Phys Chem B 2023; 127:6928-6939. [PMID: 37498794 PMCID: PMC10424244 DOI: 10.1021/acs.jpcb.3c01296] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 06/05/2023] [Indexed: 07/29/2023]
Abstract
Lipid nanoparticles (LNPs) containing ionizable aminolipids are among the leading platforms for the successful delivery of nucleic-acid-based therapeutics, including messenger RNA (mRNA). The two recently FDA-approved COVID-19 vaccines developed by Moderna and Pfizer/BioNTech belong to this category. Ionizable aminolipids, cholesterol, and DSPC lipids are among the key components of such formulations, crucially modulating physicochemical properties of these formulations and, consequently, the potency of these therapeutics. Despite the importance of these components, the distribution of these molecules in LNPs containing mRNA is not clear. In this study, we used all-atom molecular dynamics (MD) simulations to investigate the distribution and effects of the Lipid-5 (apparent pKa of the lipid nanoparticle = 6.56), a rationally designed and previously reported ionizable aminolipid by Moderna, on lipid bilayers [Mol. Ther. 2018, 26, 1509-1519]. The simulations were conducted with half of the aminolipids charged and half neutral approximately to the expected ionization in the microenvironment of the LNP surface. In all five simulated systems in this work, the cholesterol content was kept constant, whereas the DSPC and Lipid-5 concentrations were changed systematically. We found that at higher concentrations of the ionizable aminolipids, the neutral aminolipids form a disordered aggregate in the membrane interior that preferentially includes cholesterol. The rules underlying the lipid redistribution could be used to rationally choose lipids to optimize the LNP function.
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Affiliation(s)
- Sepehr Dehghani-Ghahnaviyeh
- Moderna,
Inc., Cambridge, Massachusetts 02139, United States
- Theoretical
and Computational Biophysics Group, NIH Center for Macromolecular
Modeling and Bioinformatics, Beckman Institute for Advanced Science
and Technology, Department of Biochemistry, and Center for Biophysics
and Quantitative Biology, University of
Illinois at Urbana−Champaign, Urbana, Illinois 61820, United States
| | - Michael Smith
- Moderna,
Inc., Cambridge, Massachusetts 02139, United States
| | - Yan Xia
- Moderna,
Inc., Cambridge, Massachusetts 02139, United States
| | | | - Alan Grossfield
- Department
of Biochemistry and Biophysics, University
of Rochester Medical Center, Rochester, New York 14642, United States
| | - Sreyoshi Sur
- Moderna,
Inc., Cambridge, Massachusetts 02139, United States
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11
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Tang Q, Sinclair M, Hasdemir HS, Stein R, Karakas E, Tajkhorshid E, Mchaourab H. Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.29.541986. [PMID: 37398337 PMCID: PMC10312460 DOI: 10.1101/2023.05.29.541986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
To illuminate the structural origin of catalytic asymmetry of heterodimeric ABC transporters and how it shapes the energetics of their conformational cycles, we used cryo-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy (DEER), and molecular dynamics (MD) simulations, to capture and characterize conformational states of the heterodimeric ABC multidrug exporter BmrCD in lipid nanodiscs. In addition to multiple ATP- and substrate-bound inward-facing (IF) conformations, we obtained the structure of an occluded (OC) conformation wherein the unique extracellular domain (ECD) twists to partially open the extracellular gate. In conjunction with DEER analysis of the populations of these conformations, the structures reveal that ATP-powered isomerization entails changes in the relative symmetry of the BmrC and BmrD subunits that propagates from the transmembrane domain (TMD) to the nucleotide binding domain (NBD). The structures uncover asymmetric substrate and Mg 2+ binding which we hypothesize are required for triggering ATP hydrolysis preferentially in one of the nucleotide-binding sites. MD simulations demonstrated that multiple lipid molecules, identified from the cryo-EM density maps, differentially bind the IF versus the OC conformation thus modulating their relative stability. In addition to establishing how lipid interactions with BmrCD modulate the energy landscape, our findings are framed in a distinct transport model that highlights the role of asymmetric conformations in the ATP-coupled cycle with implications to the mechanism of ABC transporters in general.
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12
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Singaram I, Sharma A, Pant S, Lihan M, Park MJ, Pergande M, Buwaneka P, Hu Y, Mahmud N, Kim YM, Cologna S, Gevorgyan V, Khan I, Tajkhorshid E, Cho W. Targeting lipid-protein interaction to treat Syk-mediated acute myeloid leukemia. Nat Chem Biol 2023; 19:239-250. [PMID: 36229686 PMCID: PMC9898191 DOI: 10.1038/s41589-022-01150-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 08/25/2022] [Indexed: 02/06/2023]
Abstract
Membrane lipids control the cellular activity of kinases containing the Src homology 2 (SH2) domain through direct lipid-SH2 domain interactions. Here we report development of new nonlipidic small molecule inhibitors of the lipid-SH2 domain interaction that block the cellular activity of their host proteins. As a pilot study, we evaluated the efficacy of lipid-SH2 domain interaction inhibitors for spleen tyrosine kinase (Syk), which is implicated in hematopoietic malignancies, including acute myeloid leukemia (AML). An optimized inhibitor (WC36) specifically and potently suppressed oncogenic activities of Syk in AML cell lines and patient-derived AML cells. Unlike ATP-competitive Syk inhibitors, WC36 was refractory to de novo and acquired drug resistance due to its ability to block not only the Syk kinase activity, but also its noncatalytic scaffolding function that is linked to drug resistance. Collectively, our study shows that targeting lipid-protein interaction is a powerful approach to developing new small molecule drugs.
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Affiliation(s)
- Indira Singaram
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Ashutosh Sharma
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Shashank Pant
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Muyun Lihan
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Mi-Jeong Park
- Department of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Melissa Pergande
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Pawanthi Buwaneka
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Yusi Hu
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Nadim Mahmud
- Department of Medicine, University of Illinois Chicago, Chicago, IL 60612, U.S.A
| | - You-Me Kim
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Stephanie Cologna
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, U.S.A
| | - Vladimir Gevorgyan
- Department of Chemistry, University of Texas at Dallas, Dallas, TX 75080, U.S.A
| | - Irum Khan
- Department of Medicine, University of Illinois Chicago, Chicago, IL 60612, U.S.A
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Wonhwa Cho
- Department of Chemistry, University of Illinois Chicago (UIC), Chicago, IL, USA.
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13
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Sarkar D, Kulke M, Vermaas JV. LongBondEliminator: A Molecular Simulation Tool to Remove Ring Penetrations in Biomolecular Simulation Systems. Biomolecules 2023; 13:biom13010107. [PMID: 36671493 PMCID: PMC9856086 DOI: 10.3390/biom13010107] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/30/2022] [Accepted: 01/01/2023] [Indexed: 01/07/2023] Open
Abstract
We develop a workflow, implemented as a plugin to the molecular visualization program VMD, that can fix ring penetrations with minimal user input. LongBondEliminator, detects ring piercing artifacts by the long, strained bonds that are the local minimum energy conformation during minimization for some assembled simulation system. The LongBondEliminator tool then automatically treats regions near these long bonds using multiple biases applied through NAMD. By combining biases implemented through the collective variables module, density-based forces, and alchemical techniques in NAMD, LongBondEliminator will iteratively alleviate long bonds found within molecular simulation systems. Through three concrete examples with increasing complexity, a lignin polymer, an viral capsid assembly, and a large, highly glycosylated protein aggrecan, we demonstrate the utility for this method in eliminating ring penetrations from classical MD simulation systems. The tool is available via gitlab as a VMD plugin, and has been developed to be generically useful across a variety of biomolecular simulations.
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14
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Trifan A, Gorgun D, Salim M, Li Z, Brace A, Zvyagin M, Ma H, Clyde A, Clark D, Hardy DJ, Burnley T, Huang L, McCalpin J, Emani M, Yoo H, Yin J, Tsaris A, Subbiah V, Raza T, Liu J, Trebesch N, Wells G, Mysore V, Gibbs T, Phillips J, Chennubhotla SC, Foster I, Stevens R, Anandkumar A, Vishwanath V, Stone JE, Tajkhorshid E, A. Harris S, Ramanathan A. Intelligent resolution: Integrating Cryo-EM with AI-driven multi-resolution simulations to observe the severe acute respiratory syndrome coronavirus-2 replication-transcription machinery in action. THE INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS 2022; 36:603-623. [PMID: 38464362 PMCID: PMC10923581 DOI: 10.1177/10943420221113513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) replication transcription complex (RTC) is a multi-domain protein responsible for replicating and transcribing the viral mRNA inside a human cell. Attacking RTC function with pharmaceutical compounds is a pathway to treating COVID-19. Conventional tools, e.g., cryo-electron microscopy and all-atom molecular dynamics (AAMD), do not provide sufficiently high resolution or timescale to capture important dynamics of this molecular machine. Consequently, we develop an innovative workflow that bridges the gap between these resolutions, using mesoscale fluctuating finite element analysis (FFEA) continuum simulations and a hierarchy of AI-methods that continually learn and infer features for maintaining consistency between AAMD and FFEA simulations. We leverage a multi-site distributed workflow manager to orchestrate AI, FFEA, and AAMD jobs, providing optimal resource utilization across HPC centers. Our study provides unprecedented access to study the SARS-CoV-2 RTC machinery, while providing general capability for AI-enabled multi-resolution simulations at scale.
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Affiliation(s)
- Anda Trifan
- Argonne National Laboratory
- University of Illinois Urbana-Champaign
| | - Defne Gorgun
- Argonne National Laboratory
- University of Illinois Urbana-Champaign
| | | | | | | | | | | | - Austin Clyde
- Argonne National Laboratory
- University of Chicago
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Ian Foster
- Argonne National Laboratory
- University of Chicago
| | - Rick Stevens
- Argonne National Laboratory
- University of Chicago
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15
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Cardoch S, Timneanu N, Caleman C, Scheicher RH. Distinguishing between Similar Miniproteins with Single-Molecule Nanopore Sensing: A Computational Study. ACS NANOSCIENCE AU 2022; 2:119-127. [PMID: 37101662 PMCID: PMC10125149 DOI: 10.1021/acsnanoscienceau.1c00022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A nanopore is a tool in single-molecule sensing biotechnology that offers label-free identification with high throughput. Nanopores have been successfully applied to sequence DNA and show potential in the study of proteins. Nevertheless, the task remains challenging due to the large variability in size, charges, and folds of proteins. Miniproteins have a small number of residues, limited secondary structure, and stable tertiary structure, which can offer a systematic way to reduce complexity. In this computational work, we theoretically evaluated sensing two miniproteins found in the human body using a silicon nitride nanopore. We employed molecular dynamics methods to compute occupied-pore ionic current magnitudes and electronic structure calculations to obtain interaction strengths between pore wall and miniprotein. From the interaction strength, we derived dwell times using a mix of combinatorics and numerical solutions. This latter approach circumvents typical computational demands needed to simulate translocation events using molecular dynamics. We focused on two miniproteins potentially difficult to distinguish owing to their isotropic geometry, similar number of residues, and overall comparable structure. We found that the occupied-pore current magnitudes not to vary significantly, but their dwell times differ by 1 order of magnitude. Together, these results suggest a successful identification protocol for similar miniproteins.
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Affiliation(s)
- Sebastian Cardoch
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Nicusor Timneanu
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Carl Caleman
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Ralph H. Scheicher
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
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16
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Thakkar R, Gajaweera S, Comer J. Organic contaminants and atmospheric nitrogen at the graphene-water interface: a simulation study. NANOSCALE ADVANCES 2022; 4:1741-1757. [PMID: 36132158 PMCID: PMC9417612 DOI: 10.1039/d1na00570g] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 03/07/2022] [Indexed: 06/15/2023]
Abstract
Ordered nanoscale patterns have been observed by atomic force microscopy at graphene-water and graphite-water interfaces. The two dominant explanations for these patterns are that (i) they consist of self-assembled organic contaminants or (ii) they are dense layers formed from atmospheric gases (especially nitrogen). Here we apply molecular dynamics simulations to study the behavior of dinitrogen and possible organic contaminants at the graphene-water interface. Despite the high concentration of N2 in ambient air, we find that its expected occupancy at the graphene-water interface is quite low. Although dense (disordered) aggregates of dinitrogen have been observed in previous simulations, our results suggest that they are stable only in the presence of supersaturated aqueous N2 solutions and dissipate rapidly when they coexist with nitrogen gas near atmospheric pressure. On the other hand, although heavy alkanes are present at only trace concentrations (micrograms per cubic meter) in typical indoor air, we predict that such concentrations can be sufficient to form ordered monolayers that cover the graphene-water interface. For octadecane, grand canonical Monte Carlo suggests nucleation and growth of monolayers above an ambient concentration near 6 μg m-3, which is less than some literature values for indoor air. The thermodynamics of the formation of these alkane monolayers includes contributions from the hydration free-energy (unfavorable), the free-energy of adsorption to the graphene-water interface (highly favorable), and integration into the alkane monolayer phase (highly favorable). Furthermore, the peak-to-peak distances in AFM force profiles perpendicular to the interface (0.43-0.53 nm), agree with the distances calculated in simulations for overlayers of alkane-like molecules, but not for molecules such as N2, water, or aromatics. Taken together, these results suggest that ordered domains observed on graphene, graphite, and other hydrophobic materials in water are consistent with alkane-like molecules occupying the interface.
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Affiliation(s)
- Ravindra Thakkar
- Nanotechnology Innovation Center of Kansas State, Department of Anatomy and Physiology 1620 Denison Avenue Mahattan Kansas USA
| | - Sandun Gajaweera
- Nanotechnology Innovation Center of Kansas State, Department of Anatomy and Physiology 1620 Denison Avenue Mahattan Kansas USA
| | - Jeffrey Comer
- Nanotechnology Innovation Center of Kansas State, Department of Anatomy and Physiology 1620 Denison Avenue Mahattan Kansas USA
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17
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Licari G, Dehghani-Ghahnaviyeh S, Tajkhorshid E. Membrane Mixer: A Toolkit for Efficient Shuffling of Lipids in Heterogeneous Biological Membranes. J Chem Inf Model 2022; 62:986-996. [PMID: 35104125 PMCID: PMC8892574 DOI: 10.1021/acs.jcim.1c01388] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular dynamics (MD) simulations of biological membranes have achieved such levels of sophistication that are commonly used to predict unresolved structures and various properties of lipids and to substantiate experimental data. While achieving sufficient sampling of lipid dynamics remains a major challenge, a commonly used method to improve lipid sampling, e.g., in terms of specific interactions with membrane-associated proteins, is to randomize the initial arrangement of lipid constituents in multiple replicas of simulations, without changing the overall lipid composition of the membrane of interest. Here, we introduce a method that can rapidly generate multiple replicas of lipid bilayers with different spatial and conformational configurations for any given lipid composition. The underlying algorithm, which allows one to shuffle lipids at any desired level, relies on the application of an external potential, here referred to as the "carving potential", that removes clashes/entanglements before lipid positions are exchanged (shuffled), thereby minimizing the energy penalty due to abrupt lipid repositioning. The method is implemented as "Membrane Mixer Plugin (MMP) 1.0" in VMD, with a convenient graphical user interface that guides the user in setting various options and parameters. The plugin is fully automated and generates new membrane replicas more rapidly and conveniently than other analogous tools. The plugin and its capabilities introduced here can be extended to include additional features in future versions.
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Affiliation(s)
- Giuseppe Licari
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States,Current address: Pharmaceutical Development Biologicals, Boehringer Ingelheim Pharmaceuticals, Inc., Biberach An Der Riß, Germany,Contributed equally to this work
| | - Sepehr Dehghani-Ghahnaviyeh
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States,Contributed equally to this work
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
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18
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Diederichs T, Ahmad K, Burns JR, Nguyen QH, Siwy ZS, Tornow M, Coveney PV, Tampé R, Howorka S. Principles of Small-Molecule Transport through Synthetic Nanopores. ACS NANO 2021; 15:16194-16206. [PMID: 34596387 DOI: 10.1021/acsnano.1c05139] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Synthetic nanopores made from DNA replicate the key biological processes of transporting molecular cargo across lipid bilayers. Understanding transport across the confined lumen of the nanopores is of fundamental interest and of relevance to their rational design for biotechnological applications. Here we reveal the transport principles of organic molecules through DNA nanopores by synergistically combining experiments and computer simulations. Using a highly parallel nanostructured platform, we synchronously measure the kinetic flux across hundreds of individual pores to obtain rate constants. The single-channel transport kinetics are close to the theoretical maximum, while selectivity is determined by the interplay of cargo charge and size, the pores' sterics and electrostatics, and the composition of the surrounding lipid bilayer. The narrow distribution of transport rates implies a high structural homogeneity of DNA nanopores. The molecular passageway through the nanopore is elucidated via coarse-grained constant-velocity steered molecular dynamics simulations. The ensemble simulations pinpoint with high resolution and statistical validity the selectivity filter within the channel lumen and determine the energetic factors governing transport. Our findings on these synthetic pores' structure-function relationship will serve to guide their rational engineering to tailor transport selectivity for cell biological research, sensing, and drug delivery.
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Affiliation(s)
- Tim Diederichs
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt/M., 60438, Germany
| | - Katya Ahmad
- Centre for Computational Science, University College London, London, WC1H0AJ, England, U.K
| | - Jonathan R Burns
- Department of Chemistry, Institute for Structural and Molecular Biology, University College London, London, WC1H0AJ, England, U.K
| | - Quoc Hung Nguyen
- Molecular Electronics, Technical University of Munich, Munich, 80333, Germany
| | - Zuzanna S Siwy
- School of Physical Sciences, University of California, Irvine, California 92697, United States
| | - Marc Tornow
- Molecular Electronics, Technical University of Munich, Munich, 80333, Germany
- Fraunhofer Research Institution for Microsystems and Solid State Technologies (EMFT), Munich, 80686, Germany
- Center of NanoScience (CeNS), Ludwig-Maximilian-University, Munich, 80539, Germany
| | - Peter V Coveney
- Centre for Computational Science, University College London, London, WC1H0AJ, England, U.K
- Informatics Institute, University of Amsterdam, Amsterdam, 1090 GH, The Netherlands
| | - Robert Tampé
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt/M., 60438, Germany
| | - Stefan Howorka
- Department of Chemistry, Institute for Structural and Molecular Biology, University College London, London, WC1H0AJ, England, U.K
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19
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Abstract
The disassembly of a viral capsid leading to the release of its genetic material into the host cell is a fundamental step in viral infection. In hepatitis B virus (HBV), the capsid consists of identical protein monomers that dimerize and then arrange themselves into pentamers or hexamers on the capsid surface. By applying atomistic molecular dynamics simulation to an entire solvated HBV capsid subjected to a uniform mechanical stress protocol, we monitor the capsid-disassembly process and analyze the process down to the level of individual amino acids in 20 independent simulation replicas. The strain of an isotropic external force, combined with structural fluctuations, causes structurally heterogeneous cracks to appear in the HBV capsid. Analysis of the monomer-monomer interfaces reveals that, in contrast to the expectation from purely mechanical considerations, the cracks mainly occur within hexameric sites, whereas pentameric sites remain largely intact. Only a small subset of the capsid protein monomers, different in each simulation, are engaged in each instance of disassembly. We identify specific residues whose interactions are most readily lost during disassembly; R127, I139, Y132, N136, A137, and V149 are among the hot spots at the interfaces between dimers that lie within hexamers, leading to disassembly. The majority of these hot-spot residues are conserved by evolution, hinting to their importance for disassembly by avoiding overstabilization of capsids.
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20
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Wilson E, Vant J, Layton J, Boyd R, Lee H, Turilli M, Hernández B, Wilkinson S, Jha S, Gupta C, Sarkar D, Singharoy A. Large-Scale Molecular Dynamics Simulations of Cellular Compartments. Methods Mol Biol 2021; 2302:335-356. [PMID: 33877636 DOI: 10.1007/978-1-0716-1394-8_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Molecular dynamics or MD simulation is gradually maturing into a tool for constructing in vivo models of living cells in atomistic details. The feasibility of such models is bolstered by integrating the simulations with data from microscopic, tomographic and spectroscopic experiments on exascale supercomputers, facilitated by the use of deep learning technologies. Over time, MD simulation has evolved from tens of thousands of atoms to over 100 million atoms comprising an entire cell organelle, a photosynthetic chromatophore vesicle from a purple bacterium. In this chapter, we present a step-by-step outline for preparing, executing and analyzing such large-scale MD simulations of biological systems that are essential to life processes. All scripts are provided via GitHub.
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Affiliation(s)
- Eric Wilson
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - John Vant
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Jacob Layton
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Ryan Boyd
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Hyungro Lee
- RADICAL, ECE, Rutgers University, Piscataway, NJ, USA
| | | | | | | | - Shantenu Jha
- RADICAL, ECE, Rutgers University, Piscataway, NJ, USA.,Brookhaven National Laboratory, Upton, NY, USA
| | - Chitrak Gupta
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA.
| | - Daipayan Sarkar
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA. .,Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
| | - Abhishek Singharoy
- The School of Molecular Sciences, Arizona State University, Tempe, AZ, USA.
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21
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Jiang W, Lin YC, Botello-Smith W, Contreras JE, Harris AL, Maragliano L, Luo YL. Free energy and kinetics of cAMP permeation through connexin26 via applied voltage and milestoning. Biophys J 2021; 120:2969-2983. [PMID: 34214529 DOI: 10.1016/j.bpj.2021.06.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/08/2021] [Accepted: 06/17/2021] [Indexed: 11/18/2022] Open
Abstract
The connexin family is a diverse group of highly regulated wide-pore channels permeable to biological signaling molecules. Despite the critical roles of connexins in mediating selective molecular signaling in health and disease, the basis of molecular permeation through these pores remains unclear. Here, we report the thermodynamics and kinetics of binding and transport of a second messenger, adenosine-3',5'-cyclophosphate (cAMP), through a connexin26 hemichannel (Cx26). First, inward and outward fluxes of cAMP molecules solvated in KCl solution were obtained from 4 μs of ± 200 mV simulations. These fluxes data yielded a single-channel permeability of cAMP and cAMP/K+ permeability ratio consistent with experimentally measured values. The results from voltage simulations were then compared with the potential of mean force (PMF) and the mean first passage times (MFPTs) of a single cAMP without voltage, obtained from a total of 16.5 μs of Voronoi-tessellated Markovian milestoning simulations. Both the voltage simulations and the milestoning simulations revealed two cAMP-binding sites, for which the binding constants KD and dissociation rates koff were computed from PMF and MFPTs. The protein dipole inside the pore produces an asymmetric PMF, reflected in unequal cAMP MFPTs in each direction once within the pore. The free energy profiles under opposite voltages were derived from the milestoning PMF and revealed the interplay between voltage and channel polarity on the total free energy. In addition, we show how these factors influence the cAMP dipole vector during permeation, and how cAMP affects the local and nonlocal pore diameter in a position-dependent manner.
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Affiliation(s)
- Wenjuan Jiang
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Yi-Chun Lin
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Wesley Botello-Smith
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Jorge E Contreras
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California.
| | - Andrew L Harris
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey.
| | - Luca Maragliano
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy; Center for Synaptic Neuroscience and Technology, Italian Institute of Technology, Genoa, Italy.
| | - Yun Lyna Luo
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California.
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22
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Mitscha-Baude G, Stadlbauer B, Howorka S, Heitzinger C. Protein Transport through Nanopores Illuminated by Long-Time-Scale Simulations. ACS NANO 2021; 15:9900-9912. [PMID: 34096722 PMCID: PMC8291773 DOI: 10.1021/acsnano.1c01078] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/28/2021] [Indexed: 06/12/2023]
Abstract
The transport of molecules through nanoscale confined space is relevant in biology, biosensing, and industrial filtration. Microscopically modeling transport through nanopores is required for a fundamental understanding and guiding engineering, but the short duration and low replica number of existing simulation approaches limit statistically relevant insight. Here we explore protein transport in nanopores with a high-throughput computational method that realistically simulates hundreds of up to seconds-long protein trajectories by combining Brownian dynamics and continuum simulation and integrating both driving forces of electroosmosis and electrophoresis. Ionic current traces are computed to enable experimental comparison. By examining three biological and synthetic nanopores, our study answers questions about the kinetics and mechanism of protein transport and additionally reveals insight that is inaccessible from experiments yet relevant for pore design. The discovery of extremely frequent unhindered passage can guide the improvement of biosensor pores to enhance desired biomolecular recognition by pore-tethered receptors. Similarly, experimentally invisible nontarget adsorption to pore walls highlights how to improve recently developed DNA nanopores. Our work can be expanded to pressure-driven flow to model industrial nanofiltration processes.
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Affiliation(s)
| | - Benjamin Stadlbauer
- Institute
of Analysis and Scientific Computing, TU
Wien, Vienna, 1040, Austria
| | - Stefan Howorka
- Department
of Chemistry, Institute of Structural Molecular Biology, University College London, London, WC1E 6BT, United Kingdom
- Institute
of Biophysics, Johannes Kepler University
Linz, Linz, 4020, Austria
| | - Clemens Heitzinger
- Institute
of Analysis and Scientific Computing, TU
Wien, Vienna, 1040, Austria
- School
of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287, United States
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23
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Wang Y, Guan X, Zhang S, Liu Y, Wang S, Fan P, Du X, Yan S, Zhang P, Chen HY, Li W, Zhang D, Huang S. Structural-profiling of low molecular weight RNAs by nanopore trapping/translocation using Mycobacterium smegmatis porin A. Nat Commun 2021; 12:3368. [PMID: 34099723 PMCID: PMC8185011 DOI: 10.1038/s41467-021-23764-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 05/06/2021] [Indexed: 12/15/2022] Open
Abstract
Folding of RNA can produce elaborate tertiary structures, corresponding to their diverse roles in the regulation of biological activities. Direct observation of RNA structures at high resolution in their native form however remains a challenge. The large vestibule and the narrow constriction of a Mycobacterium smegmatis porin A (MspA) suggests a sensing mode called nanopore trapping/translocation, which clearly distinguishes between microRNA, small interfering RNA (siRNA), transfer RNA (tRNA) and 5 S ribosomal RNA (rRNA). To further profit from the acquired event characteristics, a custom machine learning algorithm is developed. Events from measurements with a mixture of RNA analytes can be automatically classified, reporting a general accuracy of ~93.4%. tRNAs, which possess a unique tertiary structure, report a highly distinguishable sensing feature, different from all other RNA types tested in this study. With this strategy, tRNAs from different sources are measured and a high structural conservation across different species is observed in single molecule.
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MESH Headings
- Machine Learning
- MicroRNAs/chemistry
- MicroRNAs/genetics
- MicroRNAs/metabolism
- Molecular Dynamics Simulation
- Molecular Weight
- Mycobacterium smegmatis/genetics
- Mycobacterium smegmatis/metabolism
- Nanopores
- Nucleic Acid Conformation
- Porins/chemistry
- Porins/genetics
- Porins/metabolism
- RNA/chemistry
- RNA/genetics
- RNA/metabolism
- RNA Folding
- RNA Transport
- RNA, Ribosomal, 5S/chemistry
- RNA, Ribosomal, 5S/genetics
- RNA, Ribosomal, 5S/metabolism
- RNA, Small Interfering/chemistry
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
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Affiliation(s)
- Yuqin Wang
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Xiaoyu Guan
- College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, MIIT Key Laboratory of Pattern Analysis and Machine Intelligence, Nanjing, China
| | - Shanyu Zhang
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Yao Liu
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Sha Wang
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Pingping Fan
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Xiaoyu Du
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Shuanghong Yan
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
| | - Panke Zhang
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Hong-Yuan Chen
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Wenfei Li
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China
| | - Daoqiang Zhang
- College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, MIIT Key Laboratory of Pattern Analysis and Machine Intelligence, Nanjing, China
| | - Shuo Huang
- State Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing, China
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24
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Electrical unfolding of cytochrome c during translocation through a nanopore constriction. Proc Natl Acad Sci U S A 2021; 118:2016262118. [PMID: 33883276 DOI: 10.1073/pnas.2016262118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many small proteins move across cellular compartments through narrow pores. In order to thread a protein through a constriction, free energy must be overcome to either deform or completely unfold the protein. In principle, the diameter of the pore, along with the effective driving force for unfolding the protein, as well as its barrier to translocation, should be critical factors that govern whether the process proceeds via squeezing, unfolding/threading, or both. To probe this for a well-established protein system, we studied the electric-field-driven translocation behavior of cytochrome c (cyt c) through ultrathin silicon nitride (SiNx) solid-state nanopores of diameters ranging from 1.5 to 5.5 nm. For a 2.5-nm-diameter pore, we find that, in a threshold electric-field regime of ∼30 to 100 MV/m, cyt c is able to squeeze through the pore. As electric fields inside the pore are increased, the unfolded state of cyt c is thermodynamically stabilized, facilitating its translocation. In contrast, for 1.5- and 2.0-nm-diameter pores, translocation occurs only by threading of the fully unfolded protein after it transitions through a higher energy unfolding intermediate state at the mouth of the pore. The relative energies between the metastable, intermediate, and unfolded protein states are extracted using a simple thermodynamic model that is dictated by the relatively slow (∼ms) protein translocation times for passing through the nanopore. These experiments map the various modes of protein translocation through a constriction, which opens avenues for exploring protein folding structures, internal contacts, and electric-field-induced deformability.
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25
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Gorgun D, Lihan M, Kapoor K, Tajkhorshid E. Binding mode of SARS-CoV-2 fusion peptide to human cellular membrane. Biophys J 2021; 120:2914-2926. [PMID: 33675757 PMCID: PMC7929786 DOI: 10.1016/j.bpj.2021.02.041] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 01/29/2021] [Accepted: 02/15/2021] [Indexed: 01/08/2023] Open
Abstract
Infection of human cells by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) relies on its binding to a specific receptor and subsequent fusion of the viral and host cell membranes. The fusion peptide (FP), a short peptide segment in the spike protein, plays a central role in the initial penetration of the virus into the host cell membrane, followed by the fusion of the two membranes. Here, we use an array of molecular dynamics simulations that take advantage of the highly mobile membrane mimetic model to investigate the interaction of the SARS-CoV2 FP with a lipid bilayer representing mammalian cellular membranes at an atomic level and to characterize the membrane-bound form of the peptide. Six independent systems were generated by changing the initial positioning and orientation of the FP with respect to the membrane, and each system was simulated in five independent replicas, each for 300 ns. In 73% of the simulations, the FP reaches a stable, membrane-bound configuration, in which the peptide deeply penetrated into the membrane. Clustering of the results reveals three major membrane-binding modes (binding modes 1-3), in which binding mode 1 populates over half of the data points. Taking into account the sequence conservation among the viral FPs and the results of mutagenesis studies establishing the role of specific residues in the helical portion of the FP in membrane association, the significant depth of penetration of the whole peptide, and the dense population of the respective cluster, we propose that the most deeply inserted membrane-bound form (binding mode 1) represents more closely the biologically relevant form. Analysis of FP-lipid interactions shows the involvement of specific residues, previously described as the "fusion-active core residues," in membrane binding. Taken together, the results shed light on a key step involved in SARS-CoV2 infection, with potential implications in designing novel inhibitors.
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Affiliation(s)
- Defne Gorgun
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Muyun Lihan
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Karan Kapoor
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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26
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Rajeshwar T R, Anishkin A, Sukharev S, Vanegas JM. Mechanical Activation of MscL Revealed by a Locally Distributed Tension Molecular Dynamics Approach. Biophys J 2020; 120:232-242. [PMID: 33333032 DOI: 10.1016/j.bpj.2020.11.2274] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/20/2020] [Accepted: 11/30/2020] [Indexed: 02/02/2023] Open
Abstract
Membrane tension perceived by mechanosensitive (MS) proteins mediates cellular responses to mechanical stimuli and osmotic stresses, and it also guides multiple biological functions including cardiovascular control and development. In bacteria, MS channels function as tension-activated pores limiting excessive turgor pressure, with MS channel of large conductance (MscL) acting as an emergency release valve preventing cell lysis. Previous attempts to simulate gating transitions in MscL by either directly applying steering forces to the protein or by increasing the whole-system tension were not fully successful and often disrupted the integrity of the system. We present a novel, to our knowledge, locally distributed tension molecular dynamics (LDT-MD) simulation method that allows application of forces continuously distributed among lipids surrounding the channel using a specially constructed collective variable. We report reproducible and reversible transitions of MscL to the open state with measured parameters of lateral expansion and conductivity that exactly satisfy experimental values. The LDT-MD method enables exploration of the MscL-gating process with different pulling velocities and variable tension asymmetry between the inner and outer membrane leaflets. We use LDT-MD in combination with well-tempered metadynamics to reconstruct the tension-dependent free-energy landscape for the opening transition in MscL. The flexible definition of the LDT collective variable allows general application of our method to study mechanical activation of any membrane-embedded protein.
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Affiliation(s)
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, Maryland
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, Maryland
| | - Juan M Vanegas
- Department of Physics, University of Vermont, Burlington, Vermont.
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27
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Vant JW, Sarkar D, Streitwieser E, Fiorin G, Skeel R, Vermaas JV, Singharoy A. Data-guided Multi-Map variables for ensemble refinement of molecular movies. J Chem Phys 2020; 153:214102. [PMID: 33291927 PMCID: PMC7714525 DOI: 10.1063/5.0022433] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 11/09/2020] [Indexed: 12/17/2022] Open
Abstract
Driving molecular dynamics simulations with data-guided collective variables offer a promising strategy to recover thermodynamic information from structure-centric experiments. Here, the three-dimensional electron density of a protein, as it would be determined by cryo-EM or x-ray crystallography, is used to achieve simultaneously free-energy costs of conformational transitions and refined atomic structures. Unlike previous density-driven molecular dynamics methodologies that determine only the best map-model fits, our work employs the recently developed Multi-Map methodology to monitor concerted movements within equilibrium, non-equilibrium, and enhanced sampling simulations. Construction of all-atom ensembles along the chosen values of the Multi-Map variable enables simultaneous estimation of average properties, as well as real-space refinement of the structures contributing to such averages. Using three proteins of increasing size, we demonstrate that biased simulation along the reaction coordinates derived from electron densities can capture conformational transitions between known intermediates. The simulated pathways appear reversible with minimal hysteresis and require only low-resolution density information to guide the transition. The induced transitions also produce estimates for free energy differences that can be directly compared to experimental observables and population distributions. The refined model quality is superior compared to those found in the Protein Data Bank. We find that the best quantitative agreement with experimental free-energy differences is obtained using medium resolution density information coupled to comparatively large structural transitions. Practical considerations for probing the transitions between multiple intermediate density states are also discussed.
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Affiliation(s)
- John W. Vant
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, USA
| | | | - Ellen Streitwieser
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, USA
| | - Giacomo Fiorin
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20814, USA
| | - Robert Skeel
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85281, USA
| | - Josh V. Vermaas
- Computing and Computational Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Abhishek Singharoy
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, USA
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28
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Phillips JC, Hardy DJ, Maia JDC, Stone JE, Ribeiro JV, Bernardi RC, Buch R, Fiorin G, Hénin J, Jiang W, McGreevy R, Melo MCR, Radak BK, Skeel RD, Singharoy A, Wang Y, Roux B, Aksimentiev A, Luthey-Schulten Z, Kalé LV, Schulten K, Chipot C, Tajkhorshid E. Scalable molecular dynamics on CPU and GPU architectures with NAMD. J Chem Phys 2020; 153:044130. [PMID: 32752662 PMCID: PMC7395834 DOI: 10.1063/5.0014475] [Citation(s) in RCA: 1379] [Impact Index Per Article: 344.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 07/01/2020] [Indexed: 02/06/2023] Open
Abstract
NAMDis a molecular dynamics program designed for high-performance simulations of very large biological objects on CPU- and GPU-based architectures. NAMD offers scalable performance on petascale parallel supercomputers consisting of hundreds of thousands of cores, as well as on inexpensive commodity clusters commonly found in academic environments. It is written in C++ and leans on Charm++ parallel objects for optimal performance on low-latency architectures. NAMD is a versatile, multipurpose code that gathers state-of-the-art algorithms to carry out simulations in apt thermodynamic ensembles, using the widely popular CHARMM, AMBER, OPLS, and GROMOS biomolecular force fields. Here, we review the main features of NAMD that allow both equilibrium and enhanced-sampling molecular dynamics simulations with numerical efficiency. We describe the underlying concepts utilized by NAMD and their implementation, most notably for handling long-range electrostatics; controlling the temperature, pressure, and pH; applying external potentials on tailored grids; leveraging massively parallel resources in multiple-copy simulations; and hybrid quantum-mechanical/molecular-mechanical descriptions. We detail the variety of options offered by NAMD for enhanced-sampling simulations aimed at determining free-energy differences of either alchemical or geometrical transformations and outline their applicability to specific problems. Last, we discuss the roadmap for the development of NAMD and our current efforts toward achieving optimal performance on GPU-based architectures, for pushing back the limitations that have prevented biologically realistic billion-atom objects to be fruitfully simulated, and for making large-scale simulations less expensive and easier to set up, run, and analyze. NAMD is distributed free of charge with its source code at www.ks.uiuc.edu.
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Affiliation(s)
| | - David J. Hardy
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Julio D. C. Maia
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - John E. Stone
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - João V. Ribeiro
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Rafael C. Bernardi
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Giacomo Fiorin
- National Heart, Lung and Blood Institute, National
Institutes of Health, Bethesda, Maryland 20814,
USA
| | - Jérôme Hénin
- Laboratoire de Biochimie Théorique UPR 9080, CNRS
and Université de Paris, Paris, France
| | | | - Ryan McGreevy
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Brian K. Radak
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Robert D. Skeel
- School of Mathematical and Statistical Sciences,
Arizona State University, Tempe, Arizona 85281,
USA
| | - Abhishek Singharoy
- School of Molecular Sciences, Arizona State
University, Tempe, Arizona 85281, USA
| | - Yi Wang
- Department of Physics, The Chinese University of
Hong Kong, Shatin, Hong Kong, China
| | - Benoît Roux
- Department of Biochemistry, University of
Chicago, Chicago, Illinois 60637, USA
| | | | | | | | | | - Christophe Chipot
- Authors to whom correspondence should be addressed:
and . URL: http://www.ks.uiuc.edu
| | - Emad Tajkhorshid
- Authors to whom correspondence should be addressed:
and . URL: http://www.ks.uiuc.edu
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29
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Bentin J, Balme S, Picaud F. Polynucleotide differentiation using hybrid solid-state nanopore functionalizing with α-hemolysin. SOFT MATTER 2020; 16:1002-1010. [PMID: 31853534 DOI: 10.1039/c9sm01833f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report results from full atomistic molecular dynamics simulations on the properties of biomimetic nanopores. This latter result was obtained through the direct insertion of an α-hemolysin protein inside a hydrophobic solid-state nanopore. Upon translocation of different DNA strands, we demonstrate here that the theoretical system presents the same discrimination properties as the experimental one obtained previously. This opens an interesting way to promote the stability of a specific protein inside a solid nanopore to develop further biomimetic applications for DNA or protein sequencing.
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Affiliation(s)
- Jérémy Bentin
- Laboratoire de Nanomédecine, Imagerie et Thérapeutique, EA 4662, Université Bourgogne-Franche-Comté (UFR Sciences et Techniques), Centre Hospitalier Universitaire de Besançon, 16 route de Gray, 25030 Besançon, France.
| | - Sébastien Balme
- Institut Européen des Membranes, UMR5635 UM ENSCM CNRS, Place Eugène Bataillon, 34095 Montpellier cedex 5, France
| | - Fabien Picaud
- Laboratoire de Nanomédecine, Imagerie et Thérapeutique, EA 4662, Université Bourgogne-Franche-Comté (UFR Sciences et Techniques), Centre Hospitalier Universitaire de Besançon, 16 route de Gray, 25030 Besançon, France.
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30
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Singharoy A, Maffeo C, Delgado-Magnero KH, Swainsbury DJK, Sener M, Kleinekathöfer U, Vant JW, Nguyen J, Hitchcock A, Isralewitz B, Teo I, Chandler DE, Stone JE, Phillips JC, Pogorelov TV, Mallus MI, Chipot C, Luthey-Schulten Z, Tieleman DP, Hunter CN, Tajkhorshid E, Aksimentiev A, Schulten K. Atoms to Phenotypes: Molecular Design Principles of Cellular Energy Metabolism. Cell 2019; 179:1098-1111.e23. [PMID: 31730852 PMCID: PMC7075482 DOI: 10.1016/j.cell.2019.10.021] [Citation(s) in RCA: 105] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 09/04/2019] [Accepted: 10/21/2019] [Indexed: 01/01/2023]
Abstract
We report a 100-million atom-scale model of an entire cell organelle, a photosynthetic chromatophore vesicle from a purple bacterium, that reveals the cascade of energy conversion steps culminating in the generation of ATP from sunlight. Molecular dynamics simulations of this vesicle elucidate how the integral membrane complexes influence local curvature to tune photoexcitation of pigments. Brownian dynamics of small molecules within the chromatophore probe the mechanisms of directional charge transport under various pH and salinity conditions. Reproducing phenotypic properties from atomistic details, a kinetic model evinces that low-light adaptations of the bacterium emerge as a spontaneous outcome of optimizing the balance between the chromatophore's structural integrity and robust energy conversion. Parallels are drawn with the more universal mitochondrial bioenergetic machinery, from whence molecular-scale insights into the mechanism of cellular aging are inferred. Together, our integrative method and spectroscopic experiments pave the way to first-principles modeling of whole living cells.
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Affiliation(s)
- Abhishek Singharoy
- School of Molecular Sciences, Center for Applied Structural Discovery, Arizona State University at Tempe, Tempe, AZ 85282, USA.
| | - Christopher Maffeo
- Department of Physics, NSF Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Karelia H Delgado-Magnero
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - David J K Swainsbury
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Melih Sener
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Ulrich Kleinekathöfer
- Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
| | - John W Vant
- School of Molecular Sciences, Center for Applied Structural Discovery, Arizona State University at Tempe, Tempe, AZ 85282, USA
| | - Jonathan Nguyen
- School of Molecular Sciences, Center for Applied Structural Discovery, Arizona State University at Tempe, Tempe, AZ 85282, USA
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Barry Isralewitz
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Ivan Teo
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Danielle E Chandler
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - John E Stone
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - James C Phillips
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Taras V Pogorelov
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - M Ilaria Mallus
- Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
| | - Christophe Chipot
- Department of Physics, NSF Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Laboratoire International Associé CNRS-UIUC, UMR 7019, Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - Zaida Luthey-Schulten
- Department of Physics, NSF Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
| | - Emad Tajkhorshid
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Departments of Biochemistry, Chemistry, Bioengineering, and Pharmacology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Aleksei Aksimentiev
- Department of Physics, NSF Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Klaus Schulten
- Department of Physics, NSF Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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31
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Fiorin G, Marinelli F, Faraldo-Gómez JD. Direct Derivation of Free Energies of Membrane Deformation and Other Solvent Density Variations From Enhanced Sampling Molecular Dynamics. J Comput Chem 2019; 41:449-459. [PMID: 31602694 DOI: 10.1002/jcc.26075] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/04/2019] [Accepted: 08/28/2019] [Indexed: 12/20/2022]
Abstract
We report a methodology to calculate the free energy of a shape transformation in a lipid membrane directly from a molecular dynamics simulation. The bilayer need not be homogeneous or symmetric and can be atomically detailed or coarse grained. The method is based on a collective variable that quantifies the similarity between the membrane and a set of predefined density distributions. Enhanced sampling of this "Multi-Map" variable re-shapes the bilayer and permits the derivation of the corresponding potential of mean force. Calculated energies thus reflect the dynamic interplay of atoms and molecules, rather than postulated effects. Evaluation of deformations of different shape, amplitude, and range demonstrates that the macroscopic bending modulus assumed by the Helfrich-Canham model is increasingly unsuitable below the 100-Å scale. In this range of major biological significance, direct free-energy calculations reveal a much greater plasticity. We also quantify the stiffening effect of cholesterol on bilayers of different composition and compare with experiments. Lastly, we illustrate how this approach facilitates analysis of other solvent reorganization processes, such as hydrophobic hydration. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.
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Affiliation(s)
- Giacomo Fiorin
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland, 20814
| | - Fabrizio Marinelli
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland, 20814
| | - José D Faraldo-Gómez
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland, 20814
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32
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Insights into protein sequencing with an α-Hemolysin nanopore by atomistic simulations. Sci Rep 2019; 9:6440. [PMID: 31015503 PMCID: PMC6478933 DOI: 10.1038/s41598-019-42867-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/25/2019] [Indexed: 12/12/2022] Open
Abstract
Single molecule protein sequencing would represent a disruptive burst in proteomic research with important biomedical impacts. Due to their success in DNA sequencing, nanopore based devices have been recently proposed as possible tools for the sequencing of peptide chains. One of the open questions in nanopore protein sequencing concerns the ability of such devices to provide different signals for all the 20 standard amino acids. Here, using equilibrium all-atom molecular dynamics simulations, we estimated the pore clogging in α-Hemolysin nanopore associated to 20 different homopeptides, one for each standard amino acid. Our results show that pore clogging is affected by amino acid volume, hydrophobicity and net charge. The equilibrium estimations are also supported by non-equilibrium runs for calculating the current blockades for selected homopeptides. Finally, we discuss the possibility to modify the α-Hemolysin nanopore, cutting a portion of the barrel region close to the trans side, to reduce spurious signals and, hence, to enhance the sensitivity of the nanopore.
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33
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Stachiewicz A, Molski A. Sequence-Dependent Unzipping Dynamics of DNA Hairpins in a Nanopore. J Phys Chem B 2019; 123:3199-3209. [PMID: 30920837 DOI: 10.1021/acs.jpcb.9b00183] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
By applying an electric field to an insulating membrane, movement of charged particles through a nanopore can be induced. The measured ionic current reports on biomolecules passing through the nanopore. In this paper, we explore the sequence-dependent dynamics of DNA unzipping using our recently developed coarse-grained model. We estimated three molecular profiles (the potential of mean force, position-dependent diffusion coefficient, and position-dependent effective charge) for the DNA unzipping of four hairpins with different sequences. We found that the molecular profiles are correlated with the ionic current and molecular events. We also explored the unzipping kinetics using Brownian dynamics. We found that the effect of hairpin structure on the unzipping/translocation times is not only energetic (weaker hairpins unzip more quickly) but also kinetic (different unzipping and translocation pathways play an important role).
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Affiliation(s)
- Anna Stachiewicz
- Department of Chemistry , Adam Mickiewicz University , Poznan 61-614 , Poland
| | - Andrzej Molski
- Department of Chemistry , Adam Mickiewicz University , Poznan 61-614 , Poland
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34
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Pieńko T, Trylska J. Computational Methods Used to Explore Transport Events in Biological Systems. J Chem Inf Model 2019; 59:1772-1781. [DOI: 10.1021/acs.jcim.8b00974] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Tomasz Pieńko
- Centre of New Technologies, University of Warsaw, S. Banacha 2c, 02-097 Warsaw, Poland
- Department of Drug Chemistry, Faculty of Pharmacy with the Laboratory Medicine Division, Medical University of Warsaw, S. Banacha 1a, 02-097 Warsaw, Poland
| | - Joanna Trylska
- Centre of New Technologies, University of Warsaw, S. Banacha 2c, 02-097 Warsaw, Poland
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35
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Thonghin N, Kargas V, Clews J, Ford RC. Cryo-electron microscopy of membrane proteins. Methods 2018; 147:176-186. [DOI: 10.1016/j.ymeth.2018.04.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/17/2018] [Accepted: 04/20/2018] [Indexed: 10/17/2022] Open
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36
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Minh DDL. Power transformations improve interpolation of grids for molecular mechanics interaction energies. J Comput Chem 2018; 39:1200-1207. [PMID: 29457253 PMCID: PMC5995662 DOI: 10.1002/jcc.25180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 11/25/2017] [Accepted: 01/13/2018] [Indexed: 11/08/2022]
Abstract
A common strategy for speeding up molecular docking calculations is to precompute nonbonded interaction energies between a receptor molecule and a set of three-dimensional grids. The grids are then interpolated to compute energies for ligand atoms in many different binding poses. Here, I evaluate a smoothing strategy of taking a power transformation of grid point energies and inverse transformation of the result from trilinear interpolation. For molecular docking poses from 85 protein-ligand complexes, this smoothing procedure leads to significant accuracy improvements, including an approximately twofold reduction in the root mean square error at a grid spacing of 0.4 Å and retaining the ability to rank docking poses even at a grid spacing of 0.7 Å. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- David D L Minh
- Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois, 60616
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37
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Do PC, Lee EH, Le L. Steered Molecular Dynamics Simulation in Rational Drug Design. J Chem Inf Model 2018; 58:1473-1482. [DOI: 10.1021/acs.jcim.8b00261] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Phuc-Chau Do
- School of Biotechnology, International University, Vietnam National University, Ho Chi Minh City 700000, Vietnam
| | - Eric H. Lee
- Department of Medicine and Division of Hematology and Oncology, Loma Linda University Medical Center, Loma Linda, California 92350, United States
| | - Ly Le
- School of Biotechnology, International University, Vietnam National University, Ho Chi Minh City 700000, Vietnam
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38
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Chinappi M, Cecconi F. Protein sequencing via nanopore based devices: a nanofluidics perspective. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:204002. [PMID: 29595524 DOI: 10.1088/1361-648x/aababe] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Proteins perform a huge number of central functions in living organisms, thus all the new techniques allowing their precise, fast and accurate characterization at single-molecule level certainly represent a burst in proteomics with important biomedical impact. In this review, we describe the recent progresses in the developing of nanopore based devices for protein sequencing. We start with a critical analysis of the main technical requirements for nanopore protein sequencing, summarizing some ideas and methodologies that have recently appeared in the literature. In the last sections, we focus on the physical modelling of the transport phenomena occurring in nanopore based devices. The multiscale nature of the problem is discussed and, in this respect, some of the main possible computational approaches are illustrated.
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Affiliation(s)
- Mauro Chinappi
- Dipartimento di Ingegneria Industriale, Università di Roma Tor Vergata, via del Politecnico 1, 00133 Roma, Italy
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39
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Miller H, Zhou Z, Shepherd J, Wollman AJM, Leake MC. Single-molecule techniques in biophysics: a review of the progress in methods and applications. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:024601. [PMID: 28869217 DOI: 10.1088/1361-6633/aa8a02] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Single-molecule biophysics has transformed our understanding of biology, but also of the physics of life. More exotic than simple soft matter, biomatter lives far from thermal equilibrium, covering multiple lengths from the nanoscale of single molecules to up to several orders of magnitude higher in cells, tissues and organisms. Biomolecules are often characterized by underlying instability: multiple metastable free energy states exist, separated by levels of just a few multiples of the thermal energy scale k B T, where k B is the Boltzmann constant and T absolute temperature, implying complex inter-conversion kinetics in the relatively hot, wet environment of active biological matter. A key benefit of single-molecule biophysics techniques is their ability to probe heterogeneity of free energy states across a molecular population, too challenging in general for conventional ensemble average approaches. Parallel developments in experimental and computational techniques have catalysed the birth of multiplexed, correlative techniques to tackle previously intractable biological questions. Experimentally, progress has been driven by improvements in sensitivity and speed of detectors, and the stability and efficiency of light sources, probes and microfluidics. We discuss the motivation and requirements for these recent experiments, including the underpinning mathematics. These methods are broadly divided into tools which detect molecules and those which manipulate them. For the former we discuss the progress of super-resolution microscopy, transformative for addressing many longstanding questions in the life sciences, and for the latter we include progress in 'force spectroscopy' techniques that mechanically perturb molecules. We also consider in silico progress of single-molecule computational physics, and how simulation and experimentation may be drawn together to give a more complete understanding. Increasingly, combinatorial techniques are now used, including correlative atomic force microscopy and fluorescence imaging, to probe questions closer to native physiological behaviour. We identify the trade-offs, limitations and applications of these techniques, and discuss exciting new directions.
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Affiliation(s)
- Helen Miller
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
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40
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Abstract
![]()
Several apical iodide translocation
pathways have been proposed
for iodide efflux out of thyroid follicular cells, including a pathway
mediated by the sodium-coupled monocarboxylate transporter 1 (SMCT1),
which remains controversial. Herein, we evaluate structural and functional
similarities between SMCT1 and the well-studied sodium-iodide symporter
(NIS) that mediates the first step of iodide entry into the thyroid.
Free-energy calculations using a force field with electronic polarizability
verify the presence of a conserved iodide-binding pocket between the
TM2, TM3, and TM7 segments in hNIS, where iodide is coordinated by
Phe67, Gln72, Cys91, and Gln94. We demonstrate the mutation of residue
Gly93 of hNIS to a larger amino acid expels the side chain of a critical
tryptophan residue (Trp255) into the interior of the binding pocket,
partially occluding the iodide binding site and reducing iodide affinity,
which is consistent with previous reports associating mutation of
this residue with iodide uptake deficiency and hypothyroidism. Furthermore,
we find that the position of Trp255 in this hNIS mutant mirrors that
of Trp253 in wild-type hSMCT1, where a threonine (Thr91) occupies
the position homologous to that occupied by glycine in wild-type hNIS
(Gly93). Correspondingly, mutation of Thr91 to glycine in hSMCT1 makes
the pocket structure more like that of wild-type hNIS, increasing
its iodide affinity. These results suggest that wild-type hSMCT1 in
the inward-facing conformation may bind iodide only very weakly, which
may have implications for its ability to transport iodide.
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Affiliation(s)
- Ariela Vergara-Jaque
- Center for Bioinformatics and Molecular Simulation, Universidad de Talca , 2 Norte 685, Talca 3460000, Chile.,Institute of Computational Comparative Medicine, Nanotechnology Innovation Center of Kansas State, Kansas State University , Manhattan, Kansas 66506, United States
| | - Peying Fong
- Department of Anatomy and Physiology, Kansas State University College of Veterinary Medicine , Manhattan, Kansas 66506, United States
| | - Jeffrey Comer
- Institute of Computational Comparative Medicine, Nanotechnology Innovation Center of Kansas State, Kansas State University , Manhattan, Kansas 66506, United States.,Department of Anatomy and Physiology, Kansas State University College of Veterinary Medicine , Manhattan, Kansas 66506, United States
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41
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Gonzalez-Gutierrez G, Wang Y, Cymes GD, Tajkhorshid E, Grosman C. Chasing the open-state structure of pentameric ligand-gated ion channels. J Gen Physiol 2017; 149:1119-1138. [PMID: 29089419 PMCID: PMC5715906 DOI: 10.1085/jgp.201711803] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 09/14/2017] [Accepted: 10/05/2017] [Indexed: 11/25/2022] Open
Abstract
Members of the pentameric ligand-gated ion channel family have been crystallized in different conformations, including one in which the transmembrane pore is surprisingly wide. Gonzalez-Gutierrez et al. show that the open-channel conformation of animal members is more similar to the models with narrow pores. Remarkable advances have been made toward the structural characterization of ion channels in the last two decades. However, the unambiguous assignment of well-defined functional states to the obtained structural models has proved challenging. In the case of the superfamily of nicotinic-receptor channels (also referred to as pentameric ligand-gated ion channels [pLGICs]), for example, two different types of model of the open-channel conformation have been proposed on the basis of structures solved to resolutions better than 4.0 Å. At the level of the transmembrane pore, the open-state models of the proton-gated pLGIC from Gloeobacter violaceus (GLIC) and the invertebrate glutamate-gated Cl– channel (GluCl) are very similar to each other, but that of the glycine receptor (GlyR) is considerably wider. Indeed, the mean distances between the axis of ion permeation and the Cα atoms at the narrowest constriction of the pore (position −2′) differ by ∼2 Å in these two classes of model, a large difference when it comes to understanding the physicochemical bases of ion conduction and charge selectivity. Here, we take advantage of the extreme open-channel stabilizing effect of mutations at pore-facing position 9′. We find that the I9′A mutation slows down entry into desensitization of GLIC to the extent that macroscopic currents decay only slightly by the end of pH 4.5 solution applications to the extracellular side for several minutes. We crystallize (at pH 4.5) two variants of GLIC carrying this mutation and solve their structures to resolutions of 3.12 Å and 3.36 Å. Furthermore, we perform all-atom molecular dynamics simulations of ion permeation and picrotoxinin block, using the different open-channel structural models. On the basis of these results, we favor the notion that the open-channel structure of pLGICs from animals is much closer to that of the narrow models (of GLIC and GluCl) than it is to that of the GlyR.
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Affiliation(s)
| | - Yuhang Wang
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Gisela D Cymes
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Emad Tajkhorshid
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL.,Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Claudio Grosman
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL .,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL
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42
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Restrepo-Pérez L, John S, Aksimentiev A, Joo C, Dekker C. SDS-assisted protein transport through solid-state nanopores. NANOSCALE 2017; 9:11685-11693. [PMID: 28776058 PMCID: PMC5611827 DOI: 10.1039/c7nr02450a] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Using nanopores for single-molecule sequencing of proteins - similar to nanopore-based sequencing of DNA - faces multiple challenges, including unfolding of the complex tertiary structure of the proteins and enforcing their unidirectional translocation through nanopores. Here, we combine molecular dynamics (MD) simulations with single-molecule experiments to investigate the utility of SDS (Sodium Dodecyl Sulfate) to unfold proteins for solid-state nanopore translocation, while simultaneously endowing them with a stronger electrical charge. Our simulations and experiments prove that SDS-treated proteins show a considerable loss of the protein structure during the nanopore translocation. Moreover, SDS-treated proteins translocate through the nanopore in the direction prescribed by the electrophoretic force due to the negative charge impaired by SDS. In summary, our results suggest that SDS causes protein unfolding while facilitating protein translocation in the direction of the electrophoretic force; both characteristics being advantageous for future protein sequencing applications using solid-state nanopores.
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Affiliation(s)
- Laura Restrepo-Pérez
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands.
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Activation and Desensitization Mechanism of AMPA Receptor-TARP Complex by Cryo-EM. Cell 2017; 170:1234-1246.e14. [PMID: 28823560 DOI: 10.1016/j.cell.2017.07.045] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/08/2017] [Accepted: 07/25/2017] [Indexed: 11/21/2022]
Abstract
AMPA receptors mediate fast excitatory neurotransmission in the mammalian brain and transduce the binding of presynaptically released glutamate to the opening of a transmembrane cation channel. Within the postsynaptic density, however, AMPA receptors coassemble with transmembrane AMPA receptor regulatory proteins (TARPs), yielding a receptor complex with altered gating kinetics, pharmacology, and pore properties. Here, we elucidate structures of the GluA2-TARP γ2 complex in the presence of the partial agonist kainate or the full agonist quisqualate together with a positive allosteric modulator or with quisqualate alone. We show how TARPs sculpt the ligand-binding domain gating ring, enhancing kainate potency and diminishing the ensemble of desensitized states. TARPs encircle the receptor ion channel, stabilizing M2 helices and pore loops, illustrating how TARPs alter receptor pore properties. Structural and computational analysis suggests the full agonist and modulator complex harbors an ion-permeable channel gate, providing the first view of an activated AMPA receptor.
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44
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Shankla M, Aksimentiev A. Modulation of Molecular Flux Using a Graphene Nanopore Capacitor. J Phys Chem B 2017; 121:3724-3733. [PMID: 28009170 DOI: 10.1021/acs.jpcb.6b10574] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Modulation of ionic current flowing through nanoscale pores is one of the fundamental biological processes. Inspired by nature, nanopores in synthetic solid-state membranes are being developed to enable rapid analysis of biological macromolecules and to serve as elements of nanofludic circuits. Here, we theoretically investigate ion and water transport through a graphene-insulator-graphene membrane containing a single, electrolyte-filled nanopore. By means of all-atom molecular dynamics simulations, we show that the charge state of such a graphene nanopore capacitor can regulate both the selectivity and the magnitude of the nanopore ionic current. At a fixed transmembrane bias, the ionic current can be switched from being carried by an equal mixture of cations and anions to being carried almost exclusively by either cationic or anionic species, depending on the sign of the charge assigned to both plates of the capacitor. Assigning the plates of the capacitor opposite sign charges can either increase the nanopore current or reduce it substantially, depending on the polarity of the bias driving the transmembrane current. Facilitated by the changes of the nanopore surface charge, such ionic current modulations are found to occur despite the physical dimensions of the nanopore being an order of magnitude larger than the screening length of the electrolyte. The ionic current rectification is accompanied by a pronounced electro-osmotic effect that can transport neutral molecules such as proteins and drugs across the solid-state membrane and thereby serve as an interface between electronic and chemical signals.
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Affiliation(s)
- Manish Shankla
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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45
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Pud S, Chao SH, Belkin M, Verschueren D, Huijben T, van Engelenburg C, Dekker C, Aksimentiev A. Mechanical Trapping of DNA in a Double-Nanopore System. NANO LETTERS 2016; 16:8021-8028. [PMID: 27960493 PMCID: PMC5523128 DOI: 10.1021/acs.nanolett.6b04642] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Nanopores have become ubiquitous components of systems for single-molecule manipulation and detection, in particular DNA sequencing where electric field driven translocation of DNA through a nanopore is used to read out the DNA molecule. Here, we present a double-pore system where two nanopores are drilled in parallel through the same solid-state membrane, which offers new opportunities for DNA manipulation. Our experiments and molecular dynamics simulations show that simultaneous electrophoretic capture of a DNA molecule by the two nanopores mechanically traps the molecule, increasing its residence time within the nanopores by orders of magnitude. Remarkably, by using two unequal-sized nanopores, the pore of DNA entry and exit can be discerned from the ionic current blockades, and the translocation direction can be precisely controlled by small differences in the effective force applied to DNA. The mechanical arrest of DNA translocation using a double-pore system can be straightforwardly integrated into any solid-state nanopore platform, including those using optical or transverse-current readouts.
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Affiliation(s)
- Sergii Pud
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Shu-Han Chao
- Department of Physics, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Maxim Belkin
- Department of Physics, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Daniel Verschueren
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Teun Huijben
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Casper van Engelenburg
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
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46
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Yoo J, Wilson J, Aksimentiev A. Improved model of hydrated calcium ion for molecular dynamics simulations using classical biomolecular force fields. Biopolymers 2016; 105:752-63. [PMID: 27144470 PMCID: PMC4958550 DOI: 10.1002/bip.22868] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 04/26/2016] [Accepted: 04/28/2016] [Indexed: 12/16/2022]
Abstract
Calcium ions (Ca(2+) ) play key roles in various fundamental biological processes such as cell signaling and brain function. Molecular dynamics (MD) simulations have been used to study such interactions, however, the accuracy of the Ca(2+) models provided by the standard MD force fields has not been rigorously tested. Here, we assess the performance of the Ca(2+) models from the most popular classical force fields AMBER and CHARMM by computing the osmotic pressure of model compounds and the free energy of DNA-DNA interactions. In the simulations performed using the two standard models, Ca(2+) ions are seen to form artificial clusters with chloride, acetate, and phosphate species; the osmotic pressure of CaAc2 and CaCl2 solutions is a small fraction of the experimental values for both force fields. Using the standard parameterization of Ca(2+) ions in the simulations of Ca(2+) -mediated DNA-DNA interactions leads to qualitatively wrong outcomes: both AMBER and CHARMM simulations suggest strong inter-DNA attraction whereas, in experiment, DNA molecules repel one another. The artificial attraction of Ca(2+) to DNA phosphate is strong enough to affect the direction of the electric field-driven translocation of DNA through a solid-state nanopore. To address these shortcomings of the standard Ca(2+) model, we introduce a custom model of a hydrated Ca(2+) ion and show that using our model brings the results of the above MD simulations in quantitative agreement with experiment. Our improved model of Ca(2+) can be readily applied to MD simulations of various biomolecular systems, including nucleic acids, proteins and lipid bilayer membranes. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 752-763, 2016.
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Affiliation(s)
- Jejoong Yoo
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801
- Center for the Physics of Living Cells
| | - James Wilson
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801
- Center for the Physics of Living Cells
- Beckman Institute for Advanced Science and Technology
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47
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Manara RMA, Guy AT, Wallace EJ, Khalid S. Free-energy calculations reveal the subtle differences in the interactions of DNA bases with α-hemolysin. J Chem Theory Comput 2016; 11:810-6. [PMID: 26579606 DOI: 10.1021/ct501081h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Next generation DNA sequencing methods that utilize protein nanopores have the potential to revolutionize this area of biotechnology. While the technique is underpinned by simple physics, the wild-type protein pores do not have all of the desired properties for efficient and accurate DNA sequencing. Much of the research efforts have focused on protein nanopores, such as α-hemolysin from Staphylococcus aureus. However, the speed of DNA translocation has historically been an issue, hampered in part by incomplete knowledge of the energetics of translocation. Here we have utilized atomistic molecular dynamics simulations of nucleotide fragments in order to calculate the potential of mean force (PMF) through α-hemolysin. Our results reveal specific regions within the pore that play a key role in the interaction with DNA. In particular, charged residues such as D127 and K131 provide stabilizing interactions with the anionic DNA and therefore are likely to reduce the speed of translocation. These regions provide rational targets for pore optimization. Furthermore, we show that the energetic contributions to the protein-DNA interactions are a complex combination of electrostatics and short-range interactions, often mediated by water molecules.
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Affiliation(s)
- Richard M A Manara
- Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton , Southampton SO17 1BJ, United Kingdom
| | - Andrew T Guy
- Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton , Southampton SO17 1BJ, United Kingdom
| | - E Jayne Wallace
- Oxford Nanopore Technologies Ltd., Edmund Cartwright House, 4 Robert Robinson Avenue, Oxford Science Park, Oxford OX4 4GA, United Kingdom
| | - Syma Khalid
- Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton , Southampton SO17 1BJ, United Kingdom
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48
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De Biase PM, Ervin EN, Pal P, Samoylova O, Markosyan S, Keehan MG, Barrall GA, Noskov SY. What controls open-pore and residual currents in the first sensing zone of alpha-hemolysin nanopore? Combined experimental and theoretical study. NANOSCALE 2016; 8:11571-11579. [PMID: 27210516 DOI: 10.1039/c6nr00164e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The electrophoretic transport of single-stranded DNA through biological nanopores such as alpha-hemolysin (αHL) is a promising and cost-effective technology with the potential to revolutionize genomics. The rational design of pores with the controlled polymer translocation rates and high contrast between different nucleotides could improve significantly nanopore sequencing applications. Here, we apply a combination of theoretical and experimental methods in an attempt to elucidate several selective modifications in the pore which were proposed to be central for the effective discrimination between purines and pyrimidines. Our nanopore test set includes the wild type αHL and six mutants (E111N/M113X/K147N) in which the cross-section and chemical functionality of the first constriction zone of the pore are modified. Electrophysiological recordings were combined with all-atom Molecular Dynamics simulations (MD) and a recently developed Brownian Dynamics (BROMOC) protocol to investigate residual ion currents and pore-DNA interactions for two homo-polymers e.g. poly(dA)40 or poly(dC)40 blocking the pore. The calculated residual currents and contrast in the poly(dA)40/poly(dC)40 blocked pore are in qualitative agreement with the experimental recordings. We showed that a simple structural metric allows rationalization of key elements in the emergent contrast between purines and pyrimidines in the modified αHL mutants. The shape of the pore and its capacity for hydrogen bonding to a translocated polynucleotide are two essential parameters for contrast optimization. To further probe the impact of these two factors in the ssDNA sensing, we eliminated the effect of the primary constriction using serine substitutions (i.e. E111S/M113S/T145S/K147S) and increased the hydrophobic volume of the central residue in the secondary constriction (L135I). This pore modification sharply increased the contrast between Adenine (A) and Cytosine (C).
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Affiliation(s)
- Pablo M De Biase
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, AB T2N 2N4, Canada.
| | - Eric N Ervin
- Electronic BioSciences, 5754 Pacific Center Blvd., Ste. 204, San Diego, CA 92121, USA.
| | - Prithwish Pal
- Electronic BioSciences, 5754 Pacific Center Blvd., Ste. 204, San Diego, CA 92121, USA.
| | - Olga Samoylova
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, AB T2N 2N4, Canada.
| | - Suren Markosyan
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, AB T2N 2N4, Canada.
| | - Michael G Keehan
- Electronic BioSciences, 5754 Pacific Center Blvd., Ste. 204, San Diego, CA 92121, USA.
| | - Geoffrey A Barrall
- Electronic BioSciences, 5754 Pacific Center Blvd., Ste. 204, San Diego, CA 92121, USA.
| | - Sergei Yu Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, AB T2N 2N4, Canada.
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49
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McGreevy R, Teo I, Singharoy A, Schulten K. Advances in the molecular dynamics flexible fitting method for cryo-EM modeling. Methods 2016; 100:50-60. [PMID: 26804562 PMCID: PMC4848153 DOI: 10.1016/j.ymeth.2016.01.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 01/16/2016] [Accepted: 01/20/2016] [Indexed: 02/02/2023] Open
Abstract
Molecular Dynamics Flexible Fitting (MDFF) is an established technique for fitting all-atom structures of molecules into corresponding cryo-electron microscopy (cryo-EM) densities. The practical application of MDFF is simple but requires a user to be aware of and take measures against a variety of possible challenges presented by each individual case. Some of these challenges arise from the complexity of a molecular structure or the limited quality of available structural models and densities to be interpreted, while others stem from the intricacies of MDFF itself. The current article serves as an overview of the strategies that have been developed since MDFF's inception to overcome common challenges and successfully perform MDFF simulations.
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Affiliation(s)
- Ryan McGreevy
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA
| | - Ivan Teo
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Abhishek Singharoy
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA
| | - Klaus Schulten
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Stachiewicz A, Molski A. Diffusive dynamics of DNA unzipping in a nanopore. J Comput Chem 2016; 37:467-76. [PMID: 26519865 DOI: 10.1002/jcc.24236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 09/11/2015] [Accepted: 10/01/2015] [Indexed: 01/04/2023]
Abstract
When an electric field is applied to an insulating membrane, movement of charged particles through a nanopore is induced. The measured ionic current reports on biomolecules passing through the nanopore. In this work, we explored the kinetics of DNA unzipping in a nanopore using our coarse-grained model (Stachiewicz and Molski, J. Comput. Chem. 2015, 36, 947). Coarse graining allowed a more detailed analysis for a wider range of parameters than all-atom simulations. Dependence of the translocation mode (unzipping or distortion) on the pore diameter was examined, and the threshold voltages were estimated. We determined the potential of mean force, position-dependent diffusion coefficient, and position-dependent effective charge for the DNA unzipping. The three molecular profiles were correlated with the ionic current and molecular events. On the unzipping/translocation force profile, two energy maxima were found, one of them corresponding to the unzipping, and the other to the translocation barriers. The unzipping kinetics were further explored using Brownian dynamics.
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Affiliation(s)
- Anna Stachiewicz
- Department of Chemistry, Adam Mickiewicz University, Poznań, Poland
| | - Andrzej Molski
- Department of Chemistry, Adam Mickiewicz University, Poznań, Poland
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