1
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Ngo TTM, Liu B, Wang F, Basu A, Wu C, Ha T. Dependence of nucleosome mechanical stability on DNA mismatches. eLife 2024; 13:RP95514. [PMID: 38656237 DOI: 10.7554/elife.95514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024] Open
Abstract
The organization of nucleosomes into chromatin and their accessibility are shaped by local DNA mechanics. Conversely, nucleosome positions shape genetic variations, which may originate from mismatches during replication and chemical modification of DNA. To investigate how DNA mismatches affect the mechanical stability and the exposure of nucleosomal DNA, we used an optical trap combined with single-molecule FRET and a single-molecule FRET cyclization assay. We found that a single base-pair C-C mismatch enhances DNA bendability and nucleosome mechanical stability for the 601-nucleosome positioning sequence. An increase in force required for DNA unwrapping from the histone core is observed for single base-pair C-C mismatches placed at three tested positions: at the inner turn, at the outer turn, or at the junction of the inner and outer turn of the nucleosome. The results support a model where nucleosomal DNA accessibility is reduced by mismatches, potentially explaining the preferred accumulation of single-nucleotide substitutions in the nucleosome core and serving as the source of genetic variation during evolution and cancer progression. Mechanical stability of an intact nucleosome, that is mismatch-free, is also dependent on the species as we find that yeast nucleosomes are mechanically less stable and more symmetrical in the outer turn unwrapping compared to Xenopus nucleosomes.
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Affiliation(s)
- Thuy T M Ngo
- Department of Physics, Center for Physics in Living Cells University of Illinois Urbana-Champaign, Urbana, United States
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, United States
- Cancer Early Detection Advanced Research Center (CEDAR), Knight Cancer Institute, Oregon Health and Science University, Portland, United States
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, United States
- Division of Oncological Sciences, Oregon Health and Science University, Portland, United States
| | - Bailey Liu
- Department of Biophysics, Johns Hopkins University, Baltimore, United States
| | - Feng Wang
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, United States
| | - Aakash Basu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, United States
- Department of Biosciences, Durham University, Durham, United Kingdom
| | - Carl Wu
- Department of Biology, Johns Hopkins University, Baltimore, United States
- Department of Molecular Biology and Genetics, Johns Hopkins University, Baltimore, United States
| | - Taekjip Ha
- Department of Physics, Center for Physics in Living Cells University of Illinois Urbana-Champaign, Urbana, United States
- Department of Biophysics, Johns Hopkins University, Baltimore, United States
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, United States
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
- Department of Pediatrics, Harvard Medical School, Boston, United States
- Howard Hughes Medical Institute, Boston, United States
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2
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Scheuring S. Forces and energetics of the canonical tetrameric cation channel gating. Proc Natl Acad Sci U S A 2023; 120:e2221616120. [PMID: 37399394 DOI: 10.1073/pnas.2221616120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 05/15/2023] [Indexed: 07/05/2023] Open
Abstract
The canonical gating mechanism of tetrameric cation channels involves the spreading of the pore-lining helices at the so-called bundle-crossing gate. Despite a wealth of structural information, we lack a physical description of the gating process. Here, I took advantage of an entropic polymer stretching physical model and MthK structures to derive the forces and energies involved in pore-domain gating. In MthK, the Ca2+-induced conformational change in the RCK domain alone opens the bundle-crossing gate through pulling via unfolded linkers. In the open conformation, the linkers serve as entropic springs between the RCK domain and bundle-crossing gate that store an elastic potential energy of 3.6kBT and exert 9.8 pN (piconewton) radial pulling force to keep the gate open. I further derive that the work to load the linkers to prime the channel for opening is up to 3.8kBT, exerting up to 15.5 pN to pull the bundle-crossing open. Opening of the bundle-crossing leads to a release of 3.3kBT spring potential energy. Thus, the closed/RCK-apo and the open/RCK-Ca2+ conformations are separated by a barrier of several kBT. I discuss how these findings relate to the functional properties of MthK and suggest that given the architectural conservation of the helix-pore-loop-helix pore-domain among all tetrameric cation channels, these physical parameters might be quite general.
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Affiliation(s)
- Simon Scheuring
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY 10065
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY 10065
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853
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3
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Weaver DR, King GM. Atomic Force Microscopy Reveals Complexity Underlying General Secretory System Activity. Int J Mol Sci 2022; 24. [PMID: 36613499 DOI: 10.3390/ijms24010055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/24/2022] Open
Abstract
The translocation of specific polypeptide chains across membranes is an essential activity for all life forms. The main components of the general secretory (Sec) system of E. coli include integral membrane translocon SecYEG, peripheral ATPase SecA, and SecDF, an ancillary complex that enhances polypeptide secretion by coupling translocation to proton motive force. Atomic force microscopy (AFM), a single-molecule imaging technique, is well suited to unmask complex, asynchronous molecular activities of membrane-associated proteins including those comprising the Sec apparatus. Using AFM, the dynamic structure of membrane-external protein topography of Sec system components can be directly visualized with high spatial-temporal precision. This mini-review is focused on AFM imaging of the Sec system in near-native fluid conditions where activity can be maintained and biochemically verified. Angstrom-scale conformational changes of SecYEG are reported on 100 ms timescales in fluid lipid bilayers. The association of SecA with SecYEG, forming membrane-bound SecYEG/SecA translocases, is directly visualized. Recent work showing topographical aspects of the translocation process that vary with precursor species is also discussed. The data suggests that the Sec system does not employ a single translocation mechanism. We posit that differences in the spatial frequency distribution of hydrophobic content within precursor sequences may be a determining factor in mechanism selection. Precise AFM investigations of active translocases are poised to advance our currently vague understanding of the complicated macromolecular movements underlying protein export across membranes.
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4
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Seifert M, Bera SC, van Nies P, Kirchdoerfer RN, Shannon A, Le TTN, Meng X, Xia H, Wood JM, Harris LD, Papini FS, Arnold JJ, Almo S, Grove TL, Shi PY, Xiang Y, Canard B, Depken M, Cameron CE, Dulin D. Inhibition of SARS-CoV-2 polymerase by nucleotide analogs from a single-molecule perspective. eLife 2021; 10:e70968. [PMID: 34617885 PMCID: PMC8497053 DOI: 10.7554/elife.70968] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 08/24/2021] [Indexed: 12/14/2022] Open
Abstract
The absence of 'shovel-ready' anti-coronavirus drugs during vaccine development has exceedingly worsened the SARS-CoV-2 pandemic. Furthermore, new vaccine-resistant variants and coronavirus outbreaks may occur in the near future, and we must be ready to face this possibility. However, efficient antiviral drugs are still lacking to this day, due to our poor understanding of the mode of incorporation and mechanism of action of nucleotides analogs that target the coronavirus polymerase to impair its essential activity. Here, we characterize the impact of remdesivir (RDV, the only FDA-approved anti-coronavirus drug) and other nucleotide analogs (NAs) on RNA synthesis by the coronavirus polymerase using a high-throughput, single-molecule, magnetic-tweezers platform. We reveal that the location of the modification in the ribose or in the base dictates the catalytic pathway(s) used for its incorporation. We show that RDV incorporation does not terminate viral RNA synthesis, but leads the polymerase into backtrack as far as 30 nt, which may appear as termination in traditional ensemble assays. SARS-CoV-2 is able to evade the endogenously synthesized product of the viperin antiviral protein, ddhCTP, though the polymerase incorporates this NA well. This experimental paradigm is essential to the discovery and development of therapeutics targeting viral polymerases.
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Affiliation(s)
- Mona Seifert
- Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU)ErlangenGermany
| | - Subhas C Bera
- Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU)ErlangenGermany
| | - Pauline van Nies
- Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU)ErlangenGermany
| | - Robert N Kirchdoerfer
- Department of Biochemistry and Institute of Molecular Virology, University of Wisconsin-MadisonMadisonUnited States
| | - Ashleigh Shannon
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Aix-Marseille UniversitéMarseilleFrance
| | - Thi-Tuyet-Nhung Le
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Aix-Marseille UniversitéMarseilleFrance
| | - Xiangzhi Meng
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health Science Center at San AntonioSan AntonioUnited States
| | - Hongjie Xia
- Department of Biochemistry and Molecular Biology, University of Texas Medical BranchGalvestonUnited States
| | - James M Wood
- The Ferrier Research Institute, Victoria University of WellingtonWellingtonNew Zealand
| | - Lawrence D Harris
- The Ferrier Research Institute, Victoria University of WellingtonWellingtonNew Zealand
| | - Flavia S Papini
- Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU)ErlangenGermany
| | - Jamie J Arnold
- Department of Microbiology and Immunology, University of North Carolina School of MedicineChapel HillUnited States
| | - Steven Almo
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, Institute for Protein InnovationBostonUnited States
| | - Tyler L Grove
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, Institute for Protein InnovationBostonUnited States
| | - Pei-Yong Shi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Institute for Human Infections and Immunity, University of Texas Medical Branch, Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical BranchGalvestonUnited States
| | - Yan Xiang
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health Science Center at San AntonioSan AntonioUnited States
| | - Bruno Canard
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Aix-Marseille UniversitéMarseilleFrance
| | - Martin Depken
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of TechnologyDelftNetherlands
| | - Craig E Cameron
- Department of Microbiology and Immunology, University of North Carolina School of MedicineChapel HillUnited States
| | - David Dulin
- Junior Research Group 2, Interdisciplinary Center for Clinical Research, Friedrich-Alexander-University Erlangen-Nürnberg (FAU)ErlangenGermany
- Department of Physics and Astronomy, and LaserLaB Amsterdam, Vrije Universiteit AmsterdamAmsterdamNetherlands
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5
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Godoy BI, Vickers NA, Andersson SB. An Estimation Algorithm for General Linear Single Particle Tracking Models with Time-Varying Parameters. Molecules 2021; 26:886. [PMID: 33567600 PMCID: PMC7915553 DOI: 10.3390/molecules26040886] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/04/2021] [Accepted: 02/04/2021] [Indexed: 01/03/2023] Open
Abstract
Single Particle Tracking (SPT) is a powerful class of methods for studying the dynamics of biomolecules inside living cells. The techniques reveal the trajectories of individual particles, with a resolution well below the diffraction limit of light, and from them the parameters defining the motion model, such as diffusion coefficients and confinement lengths. Most existing algorithms assume these parameters are constant throughout an experiment. However, it has been demonstrated that they often vary with time as the tracked particles move through different regions in the cell or as conditions inside the cell change in response to stimuli. In this work, we propose an estimation algorithm to determine time-varying parameters of systems that discretely switch between different linear models of motion with Gaussian noise statistics, covering dynamics such as diffusion, directed motion, and Ornstein-Uhlenbeck dynamics. Our algorithm consists of three stages. In the first stage, we use a sliding window approach, combined with Expectation Maximization (EM) to determine maximum likelihood estimates of the parameters as a function of time. These results are only used to roughly estimate the number of model switches that occur in the data to guide the selection of algorithm parameters in the second stage. In the second stage, we use Change Detection (CD) techniques to identify where the models switch, taking advantage of the off-line nature of the analysis of SPT data to create non-causal algorithms with better precision than a purely causal approach. Finally, we apply EM to each set of data between the change points to determine final parameter estimates. We demonstrate our approach using experimental data generated in the lab under controlled conditions.
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Affiliation(s)
- Boris I. Godoy
- Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA; (B.I.G.); (N.A.V.)
| | - Nicholas A. Vickers
- Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA; (B.I.G.); (N.A.V.)
| | - Sean B. Andersson
- Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA; (B.I.G.); (N.A.V.)
- Division of Systems Engineering, Boston University, Boston, MA 02215, USA
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6
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Abstract
Activated protein C is a trypsin-like protease with anticoagulant and cytoprotective properties that is generated by thrombin from the zymogen precursor protein C in a reaction greatly accelerated by the cofactor thrombomodulin. The molecular details of this activation remain elusive due to the lack of structural information. We now fill this gap by providing information on the overall structural organization of these proteins using single molecule FRET and small angle X-ray scattering. Under physiological conditions, both zymogen and protease adopt a conformation with all domains vertically aligned along an axis 76 Å long and maximal particle size of 120 Å. This conformation is stabilized by binding of Ca2+ to the Gla domain and is affected minimally by interaction with thrombin. Hence, the zymogen protein C likely interacts with the thrombin-thrombomodulin complex through a rigid body association that produces a protease with essentially the same structural architecture. This scenario stands in contrast to an analogous reaction in the coagulation cascade where conversion of the zymogen prothrombin to the protease meizothrombin by the prothrombinase complex is linked to a large conformational transition of the entire protein. The presence of rigid epidermal growth factor domains in protein C as opposed to kringles in prothrombin likely accounts for the different conformational plasticity of the two zymogens. The new structural features reported here for protein C have general relevance to vitamin K-dependent clotting factors containing epidermal growth factor domains, such as factors VII, IX, and X.
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Affiliation(s)
- Bosko M Stojanovski
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Leslie A Pelc
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Xiaobing Zuo
- X-Ray Science Division, Argonne National Laboratory, Lemont, Illinois, USA
| | - Enrico Di Cera
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
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7
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Mei L, Espinosa de Los Reyes S, Reynolds MJ, Leicher R, Liu S, Alushin GM. Molecular mechanism for direct actin force-sensing by α-catenin. eLife 2020; 9:62514. [PMID: 32969337 PMCID: PMC7588232 DOI: 10.7554/elife.62514] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 09/21/2020] [Indexed: 12/13/2022] Open
Abstract
The actin cytoskeleton mediates mechanical coupling between cells and their tissue microenvironments. The architecture and composition of actin networks are modulated by force; however, it is unclear how interactions between actin filaments (F-actin) and associated proteins are mechanically regulated. Here we employ both optical trapping and biochemical reconstitution with myosin motor proteins to show single piconewton forces applied solely to F-actin enhance binding by the human version of the essential cell-cell adhesion protein αE-catenin but not its homolog vinculin. Cryo-electron microscopy structures of both proteins bound to F-actin reveal unique rearrangements that facilitate their flexible C-termini refolding to engage distinct interfaces. Truncating α-catenin’s C-terminus eliminates force-activated F-actin binding, and addition of this motif to vinculin confers force-activated binding, demonstrating that α-catenin’s C-terminus is a modular detector of F-actin tension. Our studies establish that piconewton force on F-actin can enhance partner binding, which we propose mechanically regulates cellular adhesion through α-catenin. All of the cells in our bodies rely on cues from their surrounding environment to alter their behavior. As well sending each other chemical signals, such as hormones, cells can also detect pressure and physical forces applied by the cells around them. These physical interactions are coordinated by a network of proteins called the cytoskeleton, which provide the internal scaffold that maintains a cell’s shape. However, it is not well understood how forces transmitted through the cytoskeleton are converted into mechanical signals that control cell behavior. The cytoskeleton is primarily made up protein filaments called actin, which are frequently under tension from external and internal forces that push and pull on the cell. Many proteins bind directly to actin, including adhesion proteins that allow the cell to ‘stick’ to its surroundings. One possibility is that when actin filaments feel tension, they convert this into a mechanical signal by altering how they bind to other proteins. To test this theory, Mei et al. isolated and studied an adhesion protein called α-catenin which is known to interact with actin. This revealed that when tiny forces – similar to the amount cells experience in the body – were applied to actin filaments, this caused α-catenin and actin to bind together more strongly. However, applying the same level of physical force did not alter how well actin bound to a similar adhesion protein called vinculin. Further experiments showed that this was due to differences in a small, flexible region found on both proteins. Manipulating this region revealed that it helps α-catenin attach to actin when a force is present, and was thus named a ‘force detector’. Proteins that bind to actin are essential in all animals, making it likely that force detectors are a common mechanism. Scientists can now use this discovery to identify and manipulate force detectors in other proteins across different cells and animals. This may help to develop drugs that target the mechanical signaling process, although this will require further understanding of how force detectors work at the molecular level.
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Affiliation(s)
- Lin Mei
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, United States.,Tri-Institutional PhD Program in Chemical Biology, The Rockefeller University, New York, United States
| | | | - Matthew J Reynolds
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, United States
| | - Rachel Leicher
- Tri-Institutional PhD Program in Chemical Biology, The Rockefeller University, New York, United States.,Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, United States
| | - Shixin Liu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, United States
| | - Gregory M Alushin
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, United States
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8
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Abstract
Decades of crystallographic and NMR studies have produced canonical structural models of short DNA. However, no experimental method so far has been able to test these models in vivo, where DNA is long and constrained by interactions with membranes, proteins, and other molecules. Here, we employ high-resolution frequency-modulation AFM to image single long poly(dA)-poly(dT), poly(dG)-poly(dC), and lambda DNA molecules interacting with an underlying substrate that emulates the effect of biological constraints on molecular structure. We find systematic sequence-dependent variations in groove dimensions, indicating that the structure of DNA subject to realistic interactions may differ profoundly from canonical models. These findings highlight the value of AFM as a unique, single molecule characterization tool.
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Affiliation(s)
- Kfir Kuchuk
- Department of Physics and the Russell Berrie Nanotechnology Institute , Technion - Israel Institute of Technology , Haifa 3200003 , Israel
| | - Liat Katrivas
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences and the Center of Nanoscience and Nanotechnology , Tel Aviv University , Ramat Aviv, Tel Aviv 6997801 , Israel
| | - Alexander Kotlyar
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences and the Center of Nanoscience and Nanotechnology , Tel Aviv University , Ramat Aviv, Tel Aviv 6997801 , Israel
| | - Uri Sivan
- Department of Physics and the Russell Berrie Nanotechnology Institute , Technion - Israel Institute of Technology , Haifa 3200003 , Israel
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9
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Seol Y, Harami GM, Kovács M, Neuman KC. Homology sensing via non-linear amplification of sequence-dependent pausing by RecQ helicase. eLife 2019; 8:e45909. [PMID: 31464683 PMCID: PMC6773442 DOI: 10.7554/elife.45909] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 08/28/2019] [Indexed: 12/25/2022] Open
Abstract
RecQ helicases promote genomic stability through their unique ability to suppress illegitimate recombination and resolve recombination intermediates. These DNA structure-specific activities of RecQ helicases are mediated by the helicase-and-RNAseD like C-terminal (HRDC) domain, via unknown mechanisms. Here, employing single-molecule magnetic tweezers and rapid kinetic approaches we establish that the HRDC domain stabilizes intrinsic, sequence-dependent, pauses of the core helicase (lacking the HRDC) in a DNA geometry-dependent manner. We elucidate the core unwinding mechanism in which the unwinding rate depends on the stability of the duplex DNA leading to transient sequence-dependent pauses. We further demonstrate a non-linear amplification of these transient pauses by the controlled binding of the HRDC domain. The resulting DNA sequence- and geometry-dependent pausing may underlie a homology sensing mechanism that allows rapid disruption of unstable (illegitimate) and stabilization of stable (legitimate) DNA strand invasions, which suggests an intrinsic mechanism of recombination quality control by RecQ helicases.
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Affiliation(s)
- Yeonee Seol
- Laboratory of Single Molecule BiophysicsNational Heart, Lung, and Blood Institute, National Institutes of HealthBethesdaUnited States
| | - Gábor M Harami
- Department of Biochemistry, ELTE-MTA “Momentum” Motor Enzymology Research GroupEötvös Loránd UniversityBudapestHungary
| | - Mihály Kovács
- Department of Biochemistry, ELTE-MTA “Momentum” Motor Enzymology Research GroupEötvös Loránd UniversityBudapestHungary
- Department of Biochemistry, MTA-ELTE Motor Pharmacology Research GroupEötvös Loránd UniversityBudapestHungary
| | - Keir C Neuman
- Laboratory of Single Molecule BiophysicsNational Heart, Lung, and Blood Institute, National Institutes of HealthBethesdaUnited States
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10
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Wu P, Zhang T, Liu B, Fei P, Cui L, Qin R, Zhu H, Yao D, Martinez RJ, Hu W, An C, Zhang Y, Liu J, Shi J, Fan J, Yin W, Sun J, Zhou C, Zeng X, Xu C, Wang J, Evavold BD, Zhu C, Chen W, Lou J. Mechano-regulation of Peptide-MHC Class I Conformations Determines TCR Antigen Recognition. Mol Cell 2019; 73:1015-1027.e7. [PMID: 30711376 PMCID: PMC6408234 DOI: 10.1016/j.molcel.2018.12.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 07/27/2018] [Accepted: 12/20/2018] [Indexed: 01/08/2023]
Abstract
TCRs recognize cognate pMHCs to initiate T cell signaling and adaptive immunity. Mechanical force strengthens TCR-pMHC interactions to elicit agonist-specific catch bonds to trigger TCR signaling, but the underlying dynamic structural mechanism is unclear. We combined steered molecular dynamics (SMD) simulation, single-molecule biophysical approaches, and functional assays to collectively demonstrate that mechanical force induces conformational changes in pMHCs to enhance pre-existing contacts and activates new interactions at the TCR-pMHC binding interface to resist bond dissociation under force, resulting in TCR-pMHC catch bonds and T cell activation. Intriguingly, cancer-associated somatic mutations in HLA-A2 that may restrict these conformational changes suppressed TCR-pMHC catch bonds. Structural analysis also indicated that HLA polymorphism might alter the equilibrium of these conformational changes. Our findings not only reveal critical roles of force-induced conformational changes in pMHCs for activating TCR-pMHC catch bonds but also have implications for T cell-based immunotherapy.
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Affiliation(s)
- Peng Wu
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Tongtong Zhang
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Baoyu Liu
- Coulter Department of Biomedical Engineering, Woodruff School of Mechanical Engineering, Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA; Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Panyu Fei
- School of Mechanical Engineering, Zhejiang University, Hangzhou 310058, China
| | - Lei Cui
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Rui Qin
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Huaying Zhu
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Danmei Yao
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Ryan J Martinez
- Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Wei Hu
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Chenyi An
- School of Mechanical Engineering, Zhejiang University, Hangzhou 310058, China
| | - Yong Zhang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Junwei Liu
- Key Laboratory for Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310058, China
| | - Jiawei Shi
- Key Laboratory for Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310058, China
| | - Juan Fan
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Weiwei Yin
- Key Laboratory for Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310058, China
| | - Jie Sun
- Department of Cell Biology and Bone Marrow Transplantation Center of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Chun Zhou
- School of Public Health and Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Xun Zeng
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, and First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Chenqi Xu
- State Key Laboratory of Molecular Biology, Chinese Academy Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Jianan Wang
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Brian D Evavold
- Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Cheng Zhu
- Coulter Department of Biomedical Engineering, Woodruff School of Mechanical Engineering, Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Wei Chen
- Department of Neurobiology, Institute of Neuroscience, and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China; Key Laboratory for Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310058, China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China.
| | - Jizhong Lou
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of the Chinese Academy of Sciences, Beijing 100049, China.
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11
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Zananiri R, Malik O, Rudnizky S, Gaydar V, Kreiserman R, Henn A, Kaplan A. Synergy between RecBCD subunits is essential for efficient DNA unwinding. eLife 2019; 8:e40836. [PMID: 30601118 PMCID: PMC6338465 DOI: 10.7554/elife.40836] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 01/01/2019] [Indexed: 12/12/2022] Open
Abstract
The subunits of the bacterial RecBCD act in coordination, rapidly and processively unwinding DNA at the site of a double strand break. RecBCD is able to displace DNA-binding proteins, suggesting that it generates high forces, but the specific role of each subunit in the force generation is unclear. Here, we present a novel optical tweezers assay that allows monitoring the activity of RecBCD's individual subunits, when they are part of an intact full complex. We show that RecBCD and its subunits are able to generate forces up to 25-40 pN without a significant effect on their velocity. Moreover, the isolated RecD translocates fast but is a weak helicase with limited processivity. Experiments at a broad range of [ATP] and forces suggest that RecD unwinds DNA as a Brownian ratchet, rectified by ATP binding, and that the presence of the other subunits shifts the ratchet equilibrium towards the post-translocation state.
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Affiliation(s)
- Rani Zananiri
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Omri Malik
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
- Russell Berrie Nanotechnology InstituteTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Sergei Rudnizky
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Vera Gaydar
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Roman Kreiserman
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
- Faculty of PhysicsTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Arnon Henn
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Ariel Kaplan
- Faculty of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
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12
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LeBlanc SJ, Kulkarni P, Weninger KR. Single Molecule FRET: A Powerful Tool to Study Intrinsically Disordered Proteins. Biomolecules 2018; 8:biom8040140. [PMID: 30413085 PMCID: PMC6315554 DOI: 10.3390/biom8040140] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 11/02/2018] [Accepted: 11/06/2018] [Indexed: 12/22/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are often modeled using ideas from polymer physics that suggest they smoothly explore all corners of configuration space. Experimental verification of this random, dynamic behavior is difficult as random fluctuations of IDPs cannot be synchronized across an ensemble. Single molecule fluorescence (or Förster) resonance energy transfer (smFRET) is one of the few approaches that are sensitive to transient populations of sub-states within molecular ensembles. In some implementations, smFRET has sufficient time resolution to resolve transitions in IDP behaviors. Here we present experimental issues to consider when applying smFRET to study IDP configuration. We illustrate the power of applying smFRET to IDPs by discussing two cases in the literature of protein systems for which smFRET has successfully reported phosphorylation-induced modification (but not elimination) of the disordered properties that have been connected to impacts on the related biological function. The examples we discuss, PAGE4 and a disordered segment of the GluN2B subunit of the NMDA receptor, illustrate the great potential of smFRET to inform how IDP function can be regulated by controlling the detailed ensemble of disordered states within biological networks.
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Affiliation(s)
- Sharonda J LeBlanc
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Prakash Kulkarni
- Department of Medical Oncology and Therapeutics Research, City of Hope National Medical Center, Duarte, CA 91010, USA.
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
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13
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Kim J, Shin YK. Productive and Non-productive Pathways for Synaptotagmin 1 to Support Ca 2+-Triggered Fast Exocytosis. Front Mol Neurosci 2017; 10:380. [PMID: 29187811 PMCID: PMC5695160 DOI: 10.3389/fnmol.2017.00380] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/01/2017] [Indexed: 12/17/2022] Open
Abstract
Ca2+-triggered SNARE-mediated membrane fusion is essential for neuronal communication. The speed of this process is of particular importance because it sets a time limit to cognitive and physical activities. In this work, we expand the proteoliposome-to-supported bilayer (SBL) fusion assay by successfully incorporating synaptotagmin 1 (Syt1), a major Ca2+ sensor. We report that Syt1 and Ca2+ together can elicit more than a 50-fold increase in the number of membrane fusion events when compared with membrane fusion mediated by SNAREs only. What is remarkable is that ~55% of all vesicle fusion events occurs within 20 ms upon vesicle docking. Furthermore, pre-binding of Syt1 to SNAREs prior to Ca2+ inhibits spontaneous fusion, but intriguingly, this leads to a complete loss of the Ca2+ responsiveness. Thus, our results suggest that there is a productive and a non-productive pathway for Syt1, depending on whether there is a premature interaction between Syt1 and SNAREs. Our results show that Ca2+ binding to Syt1 prior to Syt1's binding to SNAREs may be a prerequisite for the productive pathway. The successful reconstitution of Syt1 activities in the physiological time scale provides new opportunities to test the current mechanistic models for Ca2+-triggered exocytosis.
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Affiliation(s)
- Jaewook Kim
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States
| | - Yeon-Kyun Shin
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States
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14
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Rudnizky S, Malik O, Bavly A, Pnueli L, Melamed P, Kaplan A. Nucleosome mobility and the regulation of gene expression: Insights from single-molecule studies. Protein Sci 2017; 26:1266-1277. [PMID: 28329910 DOI: 10.1002/pro.3159] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/11/2017] [Accepted: 03/13/2017] [Indexed: 12/31/2022]
Abstract
Nucleosomes at the promoters of genes regulate the accessibility of the transcription machinery to DNA, and function as a basic layer in the complex regulation of gene expression. Our understanding of the role of the nucleosome's spontaneous, thermally driven position changes in modulating expression is lacking. This is the result of the paucity of experimental data on these dynamics, at high-resolution, and for DNA sequences that belong to real, transcribed genes. We have developed an assay that uses partial, reversible unzipping of nucleosomes with optical tweezers to repeatedly probe a nucleosome's position over time. Using the nucleosomes at the promoters of two model genes, Cga and Lhb, we show that the mobility of nucleosomes is modulated by the sequence of DNA and by the use of alternative histone variants, and describe how the mobility can affect transcription, at the initiation and elongation phases.
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Affiliation(s)
- Sergei Rudnizky
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Omri Malik
- Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Adaiah Bavly
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Lilach Pnueli
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Philippa Melamed
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel.,Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Ariel Kaplan
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel.,Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa, 32000, Israel
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15
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Sielaff H, Martin J, Singh D, Biuković G, Grüber G, Frasch WD. Power Stroke Angular Velocity Profiles of Archaeal A-ATP Synthase Versus Thermophilic and Mesophilic F-ATP Synthase Molecular Motors. J Biol Chem 2016; 291:25351-25363. [PMID: 27729450 PMCID: PMC5207238 DOI: 10.1074/jbc.m116.745240] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 10/03/2016] [Indexed: 01/21/2023] Open
Abstract
The angular velocities of ATPase-dependent power strokes as a function of the rotational position for the A-type molecular motor A3B3DF, from the Methanosarcina mazei Gö1 A-ATP synthase, and the thermophilic motor α3β3γ, from Geobacillus stearothermophilus (formerly known as Bacillus PS3) F-ATP synthase, are resolved at 5 μs resolution for the first time. Unexpectedly, the angular velocity profile of the A-type was closely similar in the angular positions of accelerations and decelerations to the profiles of the evolutionarily distant F-type motors of thermophilic and mesophilic origins, and they differ only in the magnitude of their velocities. M. mazei A3B3DF power strokes occurred in 120° steps at saturating ATP concentrations like the F-type motors. However, because ATP-binding dwells did not interrupt the 120° steps at limiting ATP, ATP binding to A3B3DF must occur during the catalytic dwell. Elevated concentrations of ADP did not increase dwells occurring 40° after the catalytic dwell. In F-type motors, elevated ADP induces dwells 40° after the catalytic dwell and slows the overall velocity. The similarities in these power stroke profiles are consistent with a common rotational mechanism for A-type and F-type rotary motors, in which the angular velocity is limited by the rotary position at which ATP binding occurs and by the drag imposed on the axle as it rotates within the ring of stator subunits.
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Affiliation(s)
- Hendrik Sielaff
- the School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
| | - James Martin
- From the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and
| | - Dhirendra Singh
- the School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
| | - Goran Biuković
- the School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
| | - Gerhard Grüber
- the School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
| | - Wayne D Frasch
- From the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and
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16
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Suzuki Y, Ohya S, Yamamura H, Giles WR, Imaizumi Y. A New Splice Variant of Large Conductance Ca2+-activated K+ (BK) Channel α Subunit Alters Human Chondrocyte Function. J Biol Chem 2016; 291:24247-24260. [PMID: 27758860 DOI: 10.1074/jbc.m116.743302] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 10/06/2016] [Indexed: 02/06/2023] Open
Abstract
Large conductance Ca2+-activated K+ (BK) channels play essential roles in both excitable and non-excitable cells. For example, in chondrocytes, agonist-induced Ca2+ release from intracellular store activates BK channels, and this hyperpolarizes these cells, augments Ca2+ entry, and forms a positive feed-back mechanism for Ca2+ signaling and stimulation-secretion coupling. In the present study, functional roles of a newly identified splice variant in the BK channel α subunit (BKαΔe2) were examined in a human chondrocyte cell line, OUMS-27, and in a HEK293 expression system. Although BKαΔe2 lacks exon2, which codes the intracellular S0-S1 linker (Glu-127-Leu-180), significant expression was detected in several tissues from humans and mice. Molecular image analyses revealed that BKαΔe2 channels are not expressed on plasma membrane but can traffic to the plasma membrane after forming hetero-tetramer units with wild-type BKα (BKαWT). Single-channel current analyses demonstrated that BKα hetero-tetramers containing one, two, or three BKαΔe2 subunits are functional. These hetero-tetramers have a smaller single channel conductance and exhibit lower trafficking efficiency than BKαWT homo-tetramers in a stoichiometry-dependent manner. Site-directed mutagenesis of residues in exon2 identified Helix2 and the linker to S1 (Trp-158-Leu-180, particularly Arg-178) as an essential segment for channel function including voltage dependence and trafficking. BKαΔe2 knockdown in OUMS-27 chondrocytes increased BK current density and augmented the responsiveness to histamine assayed as cyclooxygenase-2 gene expression. These findings provide significant new evidence that BKαΔe2 can modulate cellular responses to physiological stimuli in human chondrocyte and contribute under pathophysiological conditions, such as osteoarthritis.
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Affiliation(s)
- Yoshiaki Suzuki
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
| | - Susumu Ohya
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan.,the Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan, and
| | - Hisao Yamamura
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
| | - Wayne R Giles
- the Faculties of Kinesiology and Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Yuji Imaizumi
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan,
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17
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McMillan DGG, Watanabe R, Ueno H, Cook GM, Noji H. Biophysical Characterization of a Thermoalkaliphilic Molecular Motor with a High Stepping Torque Gives Insight into Evolutionary ATP Synthase Adaptation. J Biol Chem 2016; 291:23965-23977. [PMID: 27624936 DOI: 10.1074/jbc.m116.743633] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/12/2016] [Indexed: 11/06/2022] Open
Abstract
F1F0 ATP synthases are bidirectional molecular motors that translocate protons across the cell membrane by either synthesizing or hydrolyzing ATP. Alkaliphile ATP synthases are highly adapted, performing oxidative phosphorylation at high pH against an inverted pH gradient (acidin/alkalineout). Unlike mesophilic ATP synthases, alkaliphilic enzymes have tightly regulated ATP hydrolysis activity, which can be relieved in the presence of lauryldimethylamine oxide. Here, we characterized the rotary dynamics of the Caldalkalibacillus thermarum TA2.A1 F1 ATPase (TA2F1) with two forms of single molecule analysis, a magnetic bead duplex and a gold nanoparticle. TA2F1 rotated in a counterclockwise direction in both systems, adhering to Michaelis-Menten kinetics with a maximum rotation rate (Vmax) of 112.4 revolutions/s. TA2F1 displayed 120° unitary steps coupled with ATP hydrolysis. Torque measurements revealed the highest torque (52.4 piconewtons) derived from an F1 molecule using fluctuation theorem. The implications of high torque in terms of extreme environment adaptation are discussed.
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Affiliation(s)
- Duncan G G McMillan
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Rikiya Watanabe
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Hiroshi Ueno
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Gregory M Cook
- the Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, P. O. Box 56, Dunedin 9054, New Zealand
| | - Hiroyuki Noji
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
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18
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Duesterberg VK, Fischer-Hwang IT, Perez CF, Hogan DW, Block SM. Observation of long-range tertiary interactions during ligand binding by the TPP riboswitch aptamer. eLife 2015; 4. [PMID: 26709838 PMCID: PMC4775224 DOI: 10.7554/elife.12362] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/27/2015] [Indexed: 12/13/2022] Open
Abstract
The thiamine pyrophosphate (TPP) riboswitch is a cis-regulatory element in mRNA that modifies gene expression in response to TPP concentration. Its specificity is dependent upon conformational changes that take place within its aptamer domain. Here, the role of tertiary interactions in ligand binding was studied at the single-molecule level by combined force spectroscopy and Förster resonance energy transfer (smFRET), using an optical trap equipped for simultaneous smFRET. The ‘Force-FRET’ approach directly probes secondary and tertiary structural changes during folding, including events associated with binding. Concurrent transitions observed in smFRET signals and RNA extension revealed differences in helix-arm orientation between two previously-identified ligand-binding states that had been undetectable by spectroscopy alone. Our results show that the weaker binding state is able to bind to TPP, but is unable to form a tertiary docking interaction that completes the binding process. Long-range tertiary interactions stabilize global riboswitch structure and confer increased ligand specificity. DOI:http://dx.doi.org/10.7554/eLife.12362.001 When a gene is switched on, its DNA is first copied to make a molecule of messenger ribonucleic acid (mRNA). The genetic code in the mRNA is then translated into a protein. There are also untranslated regions within mRNAs that do not code for protein themselves, but serve to regulate whether or not a protein is produced from the rest of the mRNA. For example, many mRNAs contain a motif in their untranslated region called a 'riboswitch'. These motifs selectively bind to molecules that are the products of metabolic processes. One riboswitch found in bacteria, animals and plants binds to a molecule known as thiamine pyrophosphate (TPP) and regulates genes that control the uptake of a vitamin called thiamine into cells. Newly made mRNA molecules are linear strands that then fold into three-dimensional structures. The TPP riboswitch can adopt distinct shapes depending on whether it is bound to TPP or not. Knowledge of these structures is crucial for understanding how riboswitches regulate protein production. Previous research reported the folding of a TPP riboswitch from bacteria. Here, Duesterberg et al. used a combination of two techniques known as force spectroscopy and Förster resonance energy transfer (FRET) to study the folding of the TPP riboswitch from a plant called Arabidopsis thaliana. The experiments show that in the presence of TPP, structural changes occur in two arm-like appendages – known as helix arms – that extend out of the core of the riboswitch. The riboswitch adopts a particular shape when TPP is strongly bound to it, and in this shape the riboswitch can regulate the activity of certain genes. However, if the riboswitch is only weakly associated with TPP, it takes on a shape in which the two helix arms are further apart and the riboswitch is unable to form the interactions required to complete the process of binding to TPP. Duesterberg et al.’s findings reveal that the way in which the A. thaliana riboswitch changes shape when it is bound to TPP is different to that of its bacterial counterpart. The next challenge will be to observe these shape changes in even more detail, and to use these new techniques to study other riboswitches in various organisms. DOI:http://dx.doi.org/10.7554/eLife.12362.002
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Affiliation(s)
| | | | | | - Daniel W Hogan
- Department of Applied Physics, Stanford University, Stanford, United States
| | - Steven M Block
- Department of Applied Physics, Stanford University, Stanford, United States.,Department of Biology, Stanford University, Stanford, United States
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19
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Chumjan W, Winterhalter M, Schulte A, Benz R, Suginta W. Chitoporin from the Marine Bacterium Vibrio harveyi: PROBING THE ESSENTIAL ROLES OF TRP136 AT THE SURFACE OF THE CONSTRICTION ZONE. J Biol Chem 2015; 290:19184-96. [PMID: 26082491 DOI: 10.1074/jbc.m115.660530] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Indexed: 11/06/2022] Open
Abstract
VhChiP is a sugar-specific porin present in the outer membrane of the marine bacterium Vibrio harveyi. VhChiP is responsible for the uptake of chitin oligosaccharides, with particular selectivity for chitohexaose. In this study, we employed electrophysiological and biochemical approaches to demonstrate that Trp(136), located at the mouth of the VhChiP pore, plays an essential role in controlling the channel's ion conductivity, chitin affinity, and permeability. Kinetic analysis of sugar translocation obtained from single channel recordings indicated that the Trp(136) mutations W136A, W136D, W136R, and W136F considerably reduce the binding affinity of the protein channel for its best substrate, chitohexaose. Liposome swelling assays confirmed that the Trp(136) mutations decreased the rate of bulk chitohexaose permeation through the VhChiP channel. Notably, all of the mutants show increases in the off-rate for chitohexaose of up to 20-fold compared with that of the native channel. Furthermore, the cation/anion permeability ratio Pc/Pa is decreased in the W136R mutant and increased in the W136D mutant. This demonstrates that the negatively charged surface at the interior of the protein lumen preferentially attracts cationic species, leading to the cation selectivity of this trimeric channel.
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Affiliation(s)
- Watcharin Chumjan
- From the Biochemistry-Electrochemistry Research Unit, the School of Biochemistry, and
| | - Mathias Winterhalter
- the Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28759 Bremen, Germany
| | - Albert Schulte
- From the Biochemistry-Electrochemistry Research Unit, the School of Chemistry, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand and
| | - Roland Benz
- the Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28759 Bremen, Germany
| | - Wipa Suginta
- From the Biochemistry-Electrochemistry Research Unit, the School of Biochemistry, and
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20
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Gao F, Kight AD, Henderson R, Jayanthi S, Patel P, Murchison M, Sharma P, Goforth RL, Kumar TKS, Henry RL, Heyes CD. Regulation of Structural Dynamics within a Signal Recognition Particle Promotes Binding of Protein Targeting Substrates. J Biol Chem 2015; 290:15462-15474. [PMID: 25918165 DOI: 10.1074/jbc.m114.624346] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Indexed: 11/06/2022] Open
Abstract
Protein targeting is critical in all living organisms and involves a signal recognition particle (SRP), an SRP receptor, and a translocase. In co-translational targeting, interactions among these proteins are mediated by the ribosome. In chloroplasts, the light-harvesting chlorophyll-binding protein (LHCP) in the thylakoid membrane is targeted post-translationally without a ribosome. A multidomain chloroplast-specific subunit of the SRP, cpSRP43, is proposed to take on the role of coordinating the sequence of targeting events. Here, we demonstrate that cpSRP43 exhibits significant interdomain dynamics that are reduced upon binding its SRP binding partner, cpSRP54. We showed that the affinity of cpSRP43 for the binding motif of LHCP (L18) increases when cpSRP43 is complexed to the binding motif of cpSRP54 (cpSRP54pep). These results support the conclusion that substrate binding to the chloroplast SRP is modulated by protein structural dynamics in which a major role of cpSRP54 is to improve substrate binding efficiency to the cpSRP.
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Affiliation(s)
- Feng Gao
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Alicia D Kight
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | - Rory Henderson
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Srinivas Jayanthi
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Parth Patel
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Marissa Murchison
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - Priyanka Sharma
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | - Robyn L Goforth
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
| | | | - Ralph L Henry
- Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701.
| | - Colin D Heyes
- Departments of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701.
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21
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Kahn TB, Fernández JM, Perez-Jimenez R. Monitoring Oxidative Folding of a Single Protein Catalyzed by the Disulfide Oxidoreductase DsbA. J Biol Chem 2015; 290:14518-27. [PMID: 25897077 DOI: 10.1074/jbc.m115.646000] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Indexed: 12/21/2022] Open
Abstract
Oxidative folding, the process by which proteins fold and acquire disulfide bonds concurrently, is of critical importance for a wide range of biological processes. Generally, this process is catalyzed by oxidoreductase enzymes that facilitate oxidation and also bear chaperone functionality. Although this process has been well described qualitatively, fine yet important details remain obscured by a limited quantitative perspective, arising from the limitations in the application of bulk biochemical methods to the study of oxidative folding. In this work, we have applied single molecule force spectroscopy techniques to monitor in real time the process of oxidative folding as catalyzed by DsbA, the enzyme solely responsible for the catalysis of oxidative folding in the bacterial periplasm. We provide a quantitative and detailed description of the catalytic mechanism utilized by DsbA that offers insight into the entire sequence of events that occurs in the periplasm from the unfolded-reduced state to the folded-oxidized protein. We have compared our results with those of protein disulfide-isomerase, the eukaryotic counterpart of DsbA, allowing us to devise a general mechanism for oxidative folding that also reflects upon the physiological functions and demands of these enzymes in vivo.
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Affiliation(s)
- Thomas B Kahn
- From the Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, New York 10032
| | - Julio M Fernández
- Department of Biological Sciences, Columbia University, New York, New York 10027
| | - Raul Perez-Jimenez
- Centro de Investigación Cooperativa (CIC) nanoGUNE, 20018 Donostia-San Sebastian, Spain, and IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
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22
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Abstract
Myosin V and VI are antagonistic motors that cohabit membrane vesicles in cells. A systematic study of their collective function, however, is lacking and forms the focus of this study. We functionally reconstitute a two-dimensional actin-myosin interface using myosin V and VI precisely patterned on DNA nanostructures, in combination with a model keratocyte actin meshwork. While scaffolds display solely unidirectional movement, their directional flux is modulated by both actin architecture and the structural properties of the myosin lever arm. This directional flux can be finely-tuned by the relative number of myosin V and VI motors on each scaffold. Pairing computation with experimental observations suggests that the ratio of motor stall forces is a key determinant of the observed competitive outcomes. Overall, our study demonstrates an elegant mechanism for sorting of membrane cargo using equally matched antagonistic motors, simply by modulating the relative number of engagement sites for each motor type. DOI:http://dx.doi.org/10.7554/eLife.05472.001 Proteins and other molecules can be moved around a cell within bubble-like compartments called vesicles. These vesicles can travel along filaments made of a protein called actin, which forms a network that criss-crosses the cell. A family of motor proteins called myosin bind to the vesicles and are responsible for pulling them along the actin filaments. For example, myosin V pulls vesicles towards the ‘plus-end’ of the filament or the outer edges of the cell, while myosin VI pulls them in the opposite direction towards the ‘minus-end’ or the interior of the cell. Both proteins are often found on the same vesicle, and it is not clear in which direction such a vesicle will move. Hariadi et al. have shed new light on this question by sticking different combinations of myosin V and myosin VI proteins to a tiny nanostructure made of DNA and using a microscope to watch it move on actin. When a nanostructure with one myosin V and one myosin VI protein was placed on a single actin filament, it moved towards the plus-end of the filament. However, when it was placed on a two-dimensional network of actin filaments, the nanostructure was equally likely to move in either direction. Therefore, the architecture of the actin filaments influences the outcome of the competition between the two motor proteins. When both types of myosin protein were present, the nanostructure was pulled along the filament more slowly than when only one type was present. This suggests that myosin V and myosin VI are involved in a ‘tug of war’ on the actin filament. Next, Hariadi et al. altered the numbers of myosin V and myosin VI proteins on the nanostructure. The direction in which the nanostructure moved depended on the ratio of motor proteins present: when there were more myosin V proteins than myosin VI proteins, the nanostructure moved towards the plus-end, and vice versa. Hariadi et al.'s findings suggest that cells direct the movement of vesicles around a cell by altering the relative number of myosin V and myosin VI proteins bound to each vesicle. DOI:http://dx.doi.org/10.7554/eLife.05472.002
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Affiliation(s)
- Rizal F Hariadi
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Ruth F Sommese
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, United States
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23
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Abstract
Cytoplasmic dynein is a molecular motor responsible for minus-end-directed cargo transport along microtubules (MTs). Dynein motility has previously been studied on surface-immobilized MTs in vitro, which constrains the motors to move in two dimensions. In this study, we explored dynein motility in three dimensions using an MT bridge assay. We found that dynein moves in a helical trajectory around the MT, demonstrating that it generates torque during cargo transport. Unlike other cytoskeletal motors that produce torque in a specific direction, dynein generates torque in either direction, resulting in bidirectional helical motility. Dynein has a net preference to move along a right-handed helical path, suggesting that the heads tend to bind to the closest tubulin binding site in the forward direction when taking sideways steps. This bidirectional helical motility may allow dynein to avoid roadblocks in dense cytoplasmic environments during cargo transport. DOI:http://dx.doi.org/10.7554/eLife.03205.001 Cells rely on ‘molecular motors’ travelling along tracks called microtubules to move proteins and other cargoes between different parts of a cell. Dynein is a molecular motor that moves along the microtubules by taking “steps” towards the slowly growing end of these tracks. The trajectories of dynein motors have been studied extensively using techniques that can follow their movements in two dimensions. However, some molecular motors can also rotate as they travel, creating a twisting force called a torque that causes the motor to spiral around the microtubule in a helix. To assess the torque that dynein can generate and to better understand its movements in three dimensions, Can et al. used a length of microtubule to build a ‘bridge’ between two polystyrene beads. The dynein motors were made to carry a smaller polystyrene bead as cargo, and the movement of this smaller bead was tracked using a computer algorithm to interpret the motion recorded by a microscope. Can et al. found that dynein moves in a helical trajectory around the microtubule, rather than travelling along it in a straight line. As it travels it can twist in one direction or the other, generating torque in either direction. This is unlike other types of molecular motor, which produce torque in just one direction. However, dynein prefers to rotate to the right, suggesting that with every step along a microtubule, it binds to the closest available binding site in the forward direction. Why might it be useful for molecular motors to behave in this way? Can et al. propose that the ability to rotate in both directions may allow dynein to avoid roadblocks or other obstacles in the dense and busy cellular environment in which it has to operate. DOI:http://dx.doi.org/10.7554/eLife.03205.002
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Affiliation(s)
- Sinan Can
- Department of Physics, University of California, Berkeley, Berkeley, United States
| | - Mark A Dewitt
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States
| | - Ahmet Yildiz
- Department of Physics, University of California, Berkeley, Berkeley, United States Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States
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24
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Abstract
The molecular motor myosin teams up to drive muscle contraction, membrane traffic, and cell division in biological cells. Myosin function in cells emerges from the interaction of multiple motors tethered to a scaffold, with surrounding actin filaments organized into 3D networks. Despite the importance of myosin function, the influence of intermotor interactions on collective motion remains poorly understood. In this study, we used precisely engineered myosin assemblies to examine emergence in collective myosin movement. We report that tethering multiple myosin VI motors, but not myosin V motors, modifies their movement trajectories on keratocyte actin networks. Single myosin V and VI dimers display similar skewed trajectories, albeit in opposite directions, when traversing the keratocyte actin network. In contrast, tethering myosin VI motors, but not myosin V motors, progressively straightens the trajectories with increasing myosin number. Trajectory shape of multimotor scaffolds positively correlates with the stiffness of the myosin lever arm. Swapping the flexible myosin VI lever arm for the relatively rigid myosin V lever increases trajectory skewness, and vice versa. A simplified model of coupled motor movement demonstrates that the differences in flexural rigidity of the two myosin lever arms is sufficient to account for the differences in observed behavior of groups of myosin V and VI motors. In accordance with this model trajectory, shapes for scaffolds containing both myosin V and VI are dominated by the myosin with a stiffer lever arm. Our findings suggest that structural features unique to each myosin type may confer selective advantages in cellular functions.
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25
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Carrasco C, Gilhooly NS, Dillingham MS, Moreno-Herrero F. On the mechanism of recombination hotspot scanning during double-stranded DNA break resection. Proc Natl Acad Sci U S A 2013; 110:E2562-71. [PMID: 23798400 DOI: 10.1073/pnas.1303035110] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Double-stranded DNA break repair by homologous recombination is initiated by resection of free DNA ends to produce a 3'-ssDNA overhang. In bacteria, this reaction is catalyzed by helicase-nuclease complexes such as AddAB in a manner regulated by specific recombination hotspot sequences called Crossover hotspot instigator (Chi). We have used magnetic tweezers to investigate the dynamics of AddAB translocation and hotspot scanning during double-stranded DNA break resection. AddAB was prone to stochastic pausing due to transient recognition of Chi-like sequences, unveiling an antagonistic relationship between DNA translocation and sequence-specific DNA recognition. Pauses at bona fide Chi sequences were longer, were nonexponentially distributed, and resulted in an altered velocity upon restart of translocation downstream of Chi. We propose a model for the recognition of Chi sequences to explain the origin of pausing during failed and successful hotspot recognition.
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26
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McGuire H, Aurousseau MRP, Bowie D, Blunck R. Automating single subunit counting of membrane proteins in mammalian cells. J Biol Chem 2012; 287:35912-21. [PMID: 22930752 PMCID: PMC3476259 DOI: 10.1074/jbc.m112.402057] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 08/21/2012] [Indexed: 11/06/2022] Open
Abstract
Elucidating subunit stoichiometry of neurotransmitter receptors is preferably carried out in a mammalian expression system where the rules of native protein assembly are strictly obeyed. Although successful in Xenopus oocytes, single subunit counting, manually counting photobleaching steps of GFP-tagged subunits, has been hindered in mammalian cells by high background fluorescence, poor control of expression, and low GFP maturation efficiency. Here, we present a fully automated single-molecule fluorescence counting method that separates tagged proteins on the plasma membrane from background fluorescence and contaminant proteins in the cytosol or the endoplasmic reticulum and determines the protein stoichiometry. Lower GFP maturation rates observed in cells cultured at 37 °C were partly offset using a monomeric version of superfolder GFP. We were able to correctly identify the stoichiometry of GluK2 and α1 glycine receptors. Our approach permits the elucidation of stoichiometry for a wide variety of plasma membrane proteins in mammalian cells with any commercially available TIRF microscope.
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Affiliation(s)
- Hugo McGuire
- From the Groupe d'Étude des Protéines Membranaires
- Departments of Physics and
| | - Mark R. P. Aurousseau
- From the Groupe d'Étude des Protéines Membranaires
- the Department of Pharmacology and Therapeutics, McGill University, Montréal, Quebec H3G 0B1, Canada
| | - Derek Bowie
- From the Groupe d'Étude des Protéines Membranaires
- the Department of Pharmacology and Therapeutics, McGill University, Montréal, Quebec H3G 0B1, Canada
| | - Rikard Blunck
- From the Groupe d'Étude des Protéines Membranaires
- Departments of Physics and
- Physiology, Université de Montréal, Montréal, Quebec H3C 3J7 and
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27
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Maki BA, Aman TK, Amico-Ruvio SA, Kussius CL, Popescu GK. C-terminal domains of N-methyl-D-aspartic acid receptor modulate unitary channel conductance and gating. J Biol Chem 2012; 287:36071-80. [PMID: 22948148 PMCID: PMC3476275 DOI: 10.1074/jbc.m112.390013] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 08/11/2012] [Indexed: 11/06/2022] Open
Abstract
NMDA receptors (NRs) are glutamate-gated calcium-permeable channels that are essential for normal synaptic transmssion and contribute to neurodegeneration. Tetrameric proteins consist of two obligatory GluN1 (N1) and two GluN2 (N2) subunits, of which GluN2A (2A) and GluN2B (2B) are prevalent in adult brain. The intracellularly located C-terminal domains (CTDs) make a significant portion of mass of the receptors and are essential for plasticity and excitotoxicity, but their functions are incompletely defined. Recent evidence shows that truncation of the N2 CTD alters channel kinetics; however, the mechanism by which this occurs is unclear. Here we recorded activity from individual NRs lacking the CTDs of N1, 2A, or 2B and determined the gating mechanisms of these receptors. Receptors lacking the N1 CTDs had larger unitary conductance and faster deactivation kinetics, receptors lacking the 2A or 2B CTDs had longer openings and longer desensitized intervals, and the first 100 amino acids of the N2 CTD were essential for these changes. In addition, receptors lacking the CTDs of either 2A or 2B maintained isoform-specific kinetic differences and swapping CTDs between 2A and 2B had no effect on single-channel properties. Based on these results, we suggest that perturbations in the CTD can modify the NR-mediated signal in a subunit-dependent manner, in 2A these effects are most likely mediated by membrane-proximal residues, and the isoform-specific biophysical properties conferred by 2A and 2B are CTD-independent. The kinetic mechanisms we developed afford a quantitative approach to understanding how the intracellular domains of NR subunits can modulate the responses of the receptor.
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Affiliation(s)
| | - Teresa K. Aman
- the Department of Biochemistry, University at Buffalo, State University of New York, Buffalo, New York 14214
| | - Stacy A. Amico-Ruvio
- the Department of Biochemistry, University at Buffalo, State University of New York, Buffalo, New York 14214
| | - Cassandra L. Kussius
- the Department of Biochemistry, University at Buffalo, State University of New York, Buffalo, New York 14214
| | - Gabriela K. Popescu
- From the Neuroscience Program and
- the Department of Biochemistry, University at Buffalo, State University of New York, Buffalo, New York 14214
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28
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Hammerstein AF, Jayasinghe L, Bayley H. Subunit dimers of alpha-hemolysin expand the engineering toolbox for protein nanopores. J Biol Chem 2011; 286:14324-34. [PMID: 21324910 PMCID: PMC3077633 DOI: 10.1074/jbc.m111.218164] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 02/10/2011] [Indexed: 12/27/2022] Open
Abstract
Staphylococcal α-hemolysin (αHL) forms a heptameric pore that features a 14-stranded transmembrane β-barrel. We attempted to force the αHL pore to adopt novel stoichiometries by oligomerizing subunit dimers generated by in vitro transcription and translation of a tandem gene. However, in vitro transcription and translation also produced truncated proteins, monomers, that were preferentially incorporated into oligomers. These oligomers were shown to be functional heptamers by single-channel recording and had a similar mobility to wild-type heptamers in SDS-polyacrylamide gels. Purified full-length subunit dimers were then prepared by using His-tagged protein. Again, single-channel recording showed that oligomers made from these dimers are functional heptamers, implying that one or more subunits are excluded from the central pore. Therefore, the αHL pore resists all structures except those that possess seven subunits immediately surrounding the central axis. Although we were not able to change the stoichiometry of the central pore of αHL by the concatenation of subunits, we extended our findings to prepare pores containing one subunit dimer and five monomers and purified them by SDS-PAGE. Two half-chelating ligands were then installed at adjacent sites, one on each subunit of the dimer. Single-channel recording showed that pores formed from this construct formed complexes with divalent metal ions in a similar fashion to pores containing two half-chelating ligands on the same subunit, confirming that the oligomers had assembled with seven subunits around the central lumen. The ability to incorporate subunit dimers into αHL pores increases the range of structures that can be obtained from engineered protein nanopores.
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Affiliation(s)
- Anne F. Hammerstein
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Lakmal Jayasinghe
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Hagan Bayley
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
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29
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Oroz J, Valbuena A, Vera AM, Mendieta J, Gómez-Puertas P, Carrión-Vázquez M. Nanomechanics of the cadherin ectodomain: "canalization" by Ca2+ binding results in a new mechanical element. J Biol Chem 2011; 286:9405-18. [PMID: 21177864 PMCID: PMC3058956 DOI: 10.1074/jbc.m110.170399] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 12/13/2010] [Indexed: 11/06/2022] Open
Abstract
Cadherins form a large family of calcium-dependent cell-cell adhesion receptors involved in development, morphogenesis, synaptogenesis, differentiation, and carcinogenesis through signal mechanotransduction using an adaptor complex that connects them to the cytoskeleton. However, the molecular mechanisms underlying mechanotransduction through cadherins remain unknown, although their extracellular region (ectodomain) is thought to be critical in this process. By single molecule force spectroscopy, molecular dynamics simulations, and protein engineering, here we have directly examined the nanomechanics of the C-cadherin ectodomain and found it to be strongly dependent on the calcium concentration. In the presence of calcium, the ectodomain extends through a defined ("canalized") pathway that involves two mechanical resistance elements: a mechanical clamp from the cadherin domains and a novel mechanostable component from the interdomain calcium-binding regions ("calcium rivet") that is abolished by magnesium replacement and in a mutant intended to impede calcium coordination. By contrast, in the absence of calcium, the mechanical response of the ectodomain becomes largely "decanalized" and destabilized. The cadherin ectodomain may therefore behave as a calcium-switched "mechanical antenna" with very different mechanical responses depending on calcium concentration (which would affect its mechanical integrity and force transmission capability). The versatile mechanical design of the cadherin ectodomain and its dependence on extracellular calcium facilitate a variety of mechanical responses that, we hypothesize, could influence the various adhesive properties mediated by cadherins in tissue morphogenesis, synaptic plasticity, and disease. Our work represents the first step toward the mechanical characterization of the cadherin system, opening the door to understanding the mechanical bases of its mechanotransduction.
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Affiliation(s)
- Javier Oroz
- From the Instituto Cajal/Consejo Superior de Investigaciones Científicas (CSIC), Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), and Instituto Madrileño de Estudios Avanzados (IMDEA) Nanociencia, Avenida Doctor Arce 37, E-28002 Madrid, Spain
| | - Alejandro Valbuena
- From the Instituto Cajal/Consejo Superior de Investigaciones Científicas (CSIC), Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), and Instituto Madrileño de Estudios Avanzados (IMDEA) Nanociencia, Avenida Doctor Arce 37, E-28002 Madrid, Spain
| | - Andrés Manuel Vera
- From the Instituto Cajal/Consejo Superior de Investigaciones Científicas (CSIC), Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), and Instituto Madrileño de Estudios Avanzados (IMDEA) Nanociencia, Avenida Doctor Arce 37, E-28002 Madrid, Spain
| | - Jesús Mendieta
- Centro de Biología Molecular Severo Ochoa, CSIC-Universidad Autónoma de Madrid, E-28049 Madrid, Spain, and
- Biomol-Informatics SL, E-28049 Madrid, Spain
| | - Paulino Gómez-Puertas
- Centro de Biología Molecular Severo Ochoa, CSIC-Universidad Autónoma de Madrid, E-28049 Madrid, Spain, and
| | - Mariano Carrión-Vázquez
- From the Instituto Cajal/Consejo Superior de Investigaciones Científicas (CSIC), Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), and Instituto Madrileño de Estudios Avanzados (IMDEA) Nanociencia, Avenida Doctor Arce 37, E-28002 Madrid, Spain
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30
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Brameshuber M, Weghuber J, Ruprecht V, Gombos I, Horváth I, Vigh L, Eckerstorfer P, Kiss E, Stockinger H, Schütz GJ. Imaging of mobile long-lived nanoplatforms in the live cell plasma membrane. J Biol Chem 2010; 285:41765-71. [PMID: 20966075 PMCID: PMC3009904 DOI: 10.1074/jbc.m110.182121] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2010] [Revised: 10/18/2010] [Indexed: 11/06/2022] Open
Abstract
The plasma membrane has been hypothesized to contain nanoscopic lipid platforms, which are discussed in the context of "lipid rafts" or "membrane rafts." Based on biochemical and cell biological studies, rafts are believed to play a crucial role in many signaling processes. However, there is currently not much information on their size, shape, stability, surface density, composition, and heterogeneity. We present here a method that allows for the first time the direct imaging of nanoscopic long-lived platforms with raft-like properties diffusing in the live cell plasma membrane. Our method senses these platforms by their property to assemble a characteristic set of fluorescent marker proteins or lipids on a time scale of seconds. A special photobleaching protocol was used to reduce the surface density of labeled mobile platforms down to the level of well isolated diffraction-limited spots without altering the single spot brightness. The statistical distribution of probe molecules per platform was determined by single molecule brightness analysis. For demonstration, we used the consensus raft marker glycosylphosphatidylinositol-anchored monomeric GFP and the fluorescent lipid analog BODIPY-G(M1), which preferentially partitions into liquid-ordered phases. For both markers, we found cholesterol-dependent homo-association in the plasma membrane of living CHO and Jurkat T cells in the resting state, thereby demonstrating the existence of small, mobile, long-lived platforms containing these probes. We further applied the technology to address structural changes in the plasma membrane during fever-type heat shock: at elevated temperatures, the glycosylphosphatidylinositol-anchored monomeric GFP homo-association disappeared, accompanied by an increase in the expression of the small heat shock protein Hsp27.
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Affiliation(s)
- Mario Brameshuber
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Julian Weghuber
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Verena Ruprecht
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Imre Gombos
- the Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary, and
| | - Ibolya Horváth
- the Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary, and
| | - László Vigh
- the Institute of Biochemistry, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary, and
| | - Paul Eckerstorfer
- the Department of Molecular Immunology, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Lazarettgasse 19, A-1090 Vienna, Austria
| | - Endre Kiss
- the Department of Molecular Immunology, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Lazarettgasse 19, A-1090 Vienna, Austria
| | - Hannes Stockinger
- the Department of Molecular Immunology, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Lazarettgasse 19, A-1090 Vienna, Austria
| | - Gerhard J. Schütz
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
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31
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Madl J, Weghuber J, Fritsch R, Derler I, Fahrner M, Frischauf I, Lackner B, Romanin C, Schütz GJ. Resting state Orai1 diffuses as homotetramer in the plasma membrane of live mammalian cells. J Biol Chem 2010; 285:41135-42. [PMID: 20961852 PMCID: PMC3003411 DOI: 10.1074/jbc.m110.177881] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 10/05/2010] [Indexed: 01/11/2023] Open
Abstract
Store-operated calcium entry is essential for many signaling processes in nonexcitable cells. The best studied store-operated calcium current is the calcium release-activated calcium (CRAC) current in T-cells and mast cells, with Orai1 representing the essential pore forming subunit. Although it is known that functional CRAC channels in store-depleted cells are composed of four Orai1 subunits, the stoichiometric composition in quiescent cells is still discussed controversially: both a tetrameric and a dimeric stoichiometry of resting state Orai1 have been reported. We obtained here robust and similar FRET values on labeled tandem repeat constructs of Orai1 before and after store depletion, suggesting an unchanged tetrameric stoichiometry. Moreover, we directly visualized the stoichiometry of mobile Orai1 channels in live cells using a new single molecule recording modality that combines single molecule tracking and brightness analysis. By alternating imaging and photobleaching pulses, we recorded trajectories of single, fluorescently labeled Orai1 channels, with each trajectory consisting of bright and dim segments, corresponding to higher and lower numbers of colocalized active GFP label. The according brightness values were used for global fitting and statistical analysis, yielding a tetrameric subunit composition of mobile Orai1 channels in resting cells.
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Affiliation(s)
- Josef Madl
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Julian Weghuber
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Reinhard Fritsch
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Isabella Derler
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Marc Fahrner
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Irene Frischauf
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Barbara Lackner
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Christoph Romanin
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Gerhard J. Schütz
- From the Biophysics Institute, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria
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32
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Chen W, Lou J, Zhu C. Forcing switch from short- to intermediate- and long-lived states of the alphaA domain generates LFA-1/ICAM-1 catch bonds. J Biol Chem 2010; 285:35967-78. [PMID: 20819952 PMCID: PMC2975219 DOI: 10.1074/jbc.m110.155770] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 08/30/2010] [Indexed: 11/06/2022] Open
Abstract
Binding of lymphocyte function-associated antigen-1 (LFA-1) to intercellular adhesion molecule-1 (ICAM-1) mediates leukocyte adhesion under force. Using a biomembrane force probe capable of measuring single bond interactions, we showed ICAM-1 binding to LFA-1 at different conformations, including the bent conformation with the lowest affinity. We quantify how force and conformations of LFA-1 regulate its kinetics with ICAM-1. At zero-force, on-rates were substantially changed by conditions that differentially favor a bent or extended LFA-1 with a closed or open headpiece; but off-rates were identical. With increasing force, LFA-1/ICAM-1 bond lifetimes (reciprocal off-rates) first increased (catch bonds) and then decreased (slip bonds). Three states with distinct off-rates were identified from lifetime distributions. Force shifted the associated fractions from the short- to intermediate- and long-lived states, producing catch bonds at low forces, but increased their off-rates exponentially, converting catch to slip bonds at high forces. An internal ligand antagonist that blocks pulling of the α(7)-helix suppressed the intermediate-/long-lived states and eliminated catch bonds, revealing an internal catch bond between the αA and βA domains. These results elucidate an allosteric mechanism for the mechanochemistry of LFA-1/ICAM-1 binding.
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Affiliation(s)
- Wei Chen
- From the Coulter Department of Biomedical Engineering
- Woodruff School of Mechanical Engineering, and
| | - Jizhong Lou
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332 and
- the National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Cheng Zhu
- From the Coulter Department of Biomedical Engineering
- Woodruff School of Mechanical Engineering, and
- Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332 and
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33
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Haldar S, Mitra S, Chattopadhyay K. Role of protein stabilizers on the conformation of the unfolded state of cytochrome c and its early folding kinetics: investigation at single molecular resolution. J Biol Chem 2010; 285:25314-23. [PMID: 20538585 PMCID: PMC2919094 DOI: 10.1074/jbc.m110.116673] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 05/31/2010] [Indexed: 11/06/2022] Open
Abstract
An insight into the conformation and dynamics of unfolded and early intermediate states of a protein is essential to understand the mechanism of its aggregation and to design potent inhibitor molecules. Fluorescence correlation spectroscopy has been used to study the effects of several model protein stabilizers on the conformation of the unfolded state and early folding dynamics of tetramethyl rhodamine-labeled cytochrome c from Saccharomyces cerevisiae at single molecular resolution. Special attention has been given to arginine, which is a widely used stabilizer for improving refolding yield of different proteins. The value of the hydrodynamic radius (r(H)) obtained by analyzing the intensity fluctuations of the diffusing molecules has been found to increase in a two-state manner as the protein is unfolded by urea. The results further show that the presence of arginine and other protein stabilizers favors a relatively structured conformation of the unfolded states (r(H) of 29 A) over an extended one (r(H) of 40 A), which forms in their absence. Also, the time constant of a kinetic component (tau(R)) of about 30 micros has been observed by analyzing the correlation functions, which represents formation of a collapsed state. This time constant varies with urea concentration representing an inverted Chevron plot that shows a roll-over and behavior in the absence of arginine. To the best of our knowledge, this is one of the first applications of fluorescence correlation spectroscopy to study direct folding kinetics of a protein.
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Affiliation(s)
- Shubhasis Haldar
- From the Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, 4, Raja S. C. Mullick Road, Kolkata 700032, India
| | - Samaresh Mitra
- From the Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, 4, Raja S. C. Mullick Road, Kolkata 700032, India
| | - Krishnananda Chattopadhyay
- From the Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, 4, Raja S. C. Mullick Road, Kolkata 700032, India
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Tsay JM, Sippy J, delToro D, Andrews BT, Draper B, Rao V, Catalano CE, Feiss M, Smith DE. Mutations altering a structurally conserved loop-helix-loop region of a viral packaging motor change DNA translocation velocity and processivity. J Biol Chem 2010; 285:24282-9. [PMID: 20525695 PMCID: PMC2911301 DOI: 10.1074/jbc.m110.129395] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 06/03/2010] [Indexed: 11/06/2022] Open
Abstract
Many double-stranded DNA viruses employ ATP-driven motors to translocate their genomes into small, preformed viral capsids against large forces resisting confinement. Here, we show via direct single-molecule measurements that a mutation T194M downstream of the Walker B motif in the phage lambda gpA packaging motor causes an 8-fold reduction in translocation velocity without substantially changing processivity or force dependence, whereas the mutation G212S in the putative C (coupling) motif causes a 3-fold reduction in velocity and a 6-fold reduction in processivity. Meanwhile a T194M pseudorevertant (T194V) showed a near restoration of the wild-type dynamics. Structural comparisons and modeling show that these mutations are in a loop-helix-loop region that positions the key residues of the catalytic motifs, Walker B and C, in the ATPase center and is structurally homologous with analogous regions in chromosome transporters and SF2 RNA helicases. Together with recently published studies of SpoIIIE chromosome transporter and Ded1 RNA helicase mutants, these findings suggest the presence of a structurally conserved region that may be a part of the mechanism that determines motor velocity and processivity in several different types of nucleic acid translocases.
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Affiliation(s)
- James M. Tsay
- From the Department of Physics, University of California at San Diego, La Jolla, California 92093
| | - Jean Sippy
- the Department of Microbiology, University of Iowa, Iowa City, Iowa 52242
| | - Damian delToro
- From the Department of Physics, University of California at San Diego, La Jolla, California 92093
| | - Benjamin T. Andrews
- the Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, and
| | - Bonnie Draper
- the Department of Biology, Catholic University of America, Washington, D. C. 20064
| | - Venigalla Rao
- the Department of Biology, Catholic University of America, Washington, D. C. 20064
| | - Carlos E. Catalano
- the Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, and
| | - Michael Feiss
- the Department of Microbiology, University of Iowa, Iowa City, Iowa 52242
| | - Douglas E. Smith
- From the Department of Physics, University of California at San Diego, La Jolla, California 92093
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Abstract
Myosin 2 is the molecular motor in muscle. It binds actin and executes a power stroke by rotating its lever arm through an angle of approximately 70 degrees to translate actin against resistive force. Myosin 2 has evolved to function optimally under crowded conditions where rates and equilibria of macromolecular reactions undergo major shifts relative to those measured in dilute solution. Hence, an important research objective is to detect in situ the lever arm orientation. Single-molecule measurements are preferred because they clarify ambiguities that are unavoidable with ensemble measurements; however, detecting single molecules in the condensed tissue medium where the myosin concentration exceeds 100 muM is challenging. A myosin light chain (MLC) tagged with photoactivatable green fluorescent protein (PAGFP) was constructed. The recombinant MLC physically and functionally replaced native MLC on the myosin lever arm in a permeabilized skeletal muscle fiber. Probe illumination volume was minimized using total internal reflection fluorescence microscopy, and PAGFP was sparsely photoactivated such that polarized fluorescence identified a single probe orientation. Several physiological states of the muscle fiber were characterized, revealing two distinct orientation populations in all states called straight and bent conformations. Conformation occupancy probability varies among fiber states with rigor and isometric contraction at extremes where straight and bent conformations predominate, respectively. Comparison to previous work on single rigor cross-bridges at the A-band periphery where the myosin concentration is low suggests molecular crowding in the A-band promotes occupancy of the straight myosin conformation [Burghardt, T. P., et al. (2007) Biophys. J. 93, 2226]. The latter may have a role in contraction because it provides additional free energy favoring completion of the cross-bridge power stroke.
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Affiliation(s)
- Thomas P Burghardt
- Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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