101
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Schuler B. Perspective: Chain dynamics of unfolded and intrinsically disordered proteins from nanosecond fluorescence correlation spectroscopy combined with single-molecule FRET. J Chem Phys 2018; 149:010901. [PMID: 29981536 DOI: 10.1063/1.5037683] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The dynamics of unfolded proteins are important both for the process of protein folding and for the behavior of intrinsically disordered proteins. However, methods for investigating the global chain dynamics of these structurally diverse systems have been limited. A versatile experimental approach is single-molecule spectroscopy in combination with Förster resonance energy transfer and nanosecond fluorescence correlation spectroscopy. The concepts of polymer physics offer a powerful framework both for interpreting the results and for understanding and classifying the properties of unfolded and intrinsically disordered proteins. This information on long-range chain dynamics can be complemented with spectroscopic techniques that probe different length scales and time scales, and integration of these results greatly benefits from recent advances in molecular simulations. This increasing convergence between the experiment, theory, and simulation is thus starting to enable an increasingly detailed view of the dynamics of disordered proteins.
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Affiliation(s)
- Benjamin Schuler
- Department of Biochemistry and Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
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102
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Satija R, Das A, Makarov DE. Transition path times reveal memory effects and anomalous diffusion in the dynamics of protein folding. J Chem Phys 2018; 147:152707. [PMID: 29055292 DOI: 10.1063/1.4993228] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Recent single-molecule experiments probed transition paths of biomolecular folding and, in particular, measured the time biomolecules spend while crossing their free energy barriers. A surprising finding from these studies is that the transition barriers crossed by transition paths, as inferred from experimentally observed transition path times, are often lower than the independently determined free energy barriers. Here we explore memory effects leading to anomalous diffusion as a possible origin of this discrepancy. Our analysis of several molecular dynamics trajectories shows that the dynamics of common reaction coordinates used to describe protein folding is subdiffusive, at least at sufficiently short times. We capture this effect using a one-dimensional fractional Brownian motion (FBM) model, in which the system undergoes a subdiffusive process in the presence of a potential of mean force, and show that this model yields much broader distributions of transition path times with stretched exponential long-time tails. Without any adjustable parameters, these distributions agree well with the transition path times computed directly from protein trajectories. We further discuss how the FBM model can be tested experimentally.
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Affiliation(s)
- Rohit Satija
- Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas 78712, USA
| | - Atanu Das
- Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas 78712, USA
| | - Dmitrii E Makarov
- Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas 78712, USA
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103
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Berezhkovskii AM, Makarov DE. Communication: Coordinate-dependent diffusivity from single molecule trajectories. J Chem Phys 2018; 147:201102. [PMID: 29195291 DOI: 10.1063/1.5006456] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Single-molecule observations of biomolecular folding are commonly interpreted using the model of one-dimensional diffusion along a reaction coordinate, with a coordinate-independent diffusion coefficient. Recent analysis, however, suggests that more general models are required to account for single-molecule measurements performed with high temporal resolution. Here, we consider one such generalization: a model where the diffusion coefficient can be an arbitrary function of the reaction coordinate. Assuming Brownian dynamics along this coordinate, we derive an exact expression for the coordinate-dependent diffusivity in terms of the splitting probability within an arbitrarily chosen interval and the mean transition path time between the interval boundaries. This formula can be used to estimate the effective diffusion coefficient along a reaction coordinate directly from single-molecule trajectories.
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Affiliation(s)
- Alexander M Berezhkovskii
- Mathematical and Statistical Computing Laboratory, Office of Intramural Research, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Dmitrii E Makarov
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
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104
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Hadzic MCAS, Börner R, König SLB, Kowerko D, Sigel RKO. Reliable State Identification and State Transition Detection in Fluorescence Intensity-Based Single-Molecule Förster Resonance Energy-Transfer Data. J Phys Chem B 2018; 122:6134-6147. [PMID: 29737844 DOI: 10.1021/acs.jpcb.7b12483] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a powerful technique to probe biomolecular structure and dynamics. A popular implementation of smFRET consists of recording fluorescence intensity time traces of surface-immobilized, chromophore-tagged molecules. This approach generates large and complex data sets, the analysis of which is to date not standardized. Here, we address a key challenge in smFRET data analysis: the generation of thermodynamic and kinetic models that describe with statistical rigor the behavior of FRET trajectories recorded from surface-tethered biomolecules in terms of the number of FRET states, the corresponding mean FRET values, and the kinetic rates at which they interconvert. For this purpose, we first perform Monte Carlo simulations to generate smFRET trajectories, in which a relevant space of experimental parameters is explored. Then, we provide an account on current strategies to achieve such model selection, as well as a quantitative assessment of their performances. Specifically, we evaluate the performance of each algorithm (change-point analysis, STaSI, HaMMy, vbFRET, and ebFRET) with respect to accuracy, reproducibility, and computing time, which yields a range of algorithm-specific referential benchmarks for various data qualities. Data simulation and analysis were performed with our MATLAB-based multifunctional analysis software for handling smFRET data (MASH-FRET).
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Affiliation(s)
| | | | | | - Danny Kowerko
- Department of Computer Science , Chemnitz University of Technology , 09111 Chemnitz , Germany
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105
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Lee TC, Moran CR, Cistrone PA, Dawson PE, Deniz AA. Site-Specific Three-Color Labeling of α-Synuclein via Conjugation to Uniquely Reactive Cysteines during Assembly by Native Chemical Ligation. Cell Chem Biol 2018; 25:797-801.e4. [PMID: 29681525 DOI: 10.1016/j.chembiol.2018.03.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/09/2017] [Accepted: 03/22/2018] [Indexed: 12/15/2022]
Abstract
Single-molecule fluorescence is widely used to study conformational complexity in proteins, and has proven especially valuable with intrinsically disordered proteins (IDPs). Protein studies using dual-color single-molecule Förster resonance energy transfer (smFRET) are now quite common, but many could benefit from simultaneous measurement of multiple distances through multi-color labeling. Such studies, however, have suffered from limitations in site-specific incorporation of more than two dyes per polypeptide. Here we present a fully site-specific three-color labeling scheme for α-synuclein, an IDP with important putative functions and links to Parkinson disease. The convergent synthesis combines native chemical ligation with regiospecific cysteine protection of expressed protein fragments to permit highly controlled labeling via standard cysteine-maleimide chemistry, enabling more global smFRET studies. Furthermore, this modular approach is generally compatible with recombinant proteins and expandable to accommodate even more complex experiments, such as by labeling with additional colors.
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Affiliation(s)
- Taehyung C Lee
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Crystal R Moran
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Philip A Cistrone
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Philip E Dawson
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Ashok A Deniz
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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106
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Börner R, Kowerko D, Hadzic MCAS, König SLB, Ritter M, Sigel RKO. Simulations of camera-based single-molecule fluorescence experiments. PLoS One 2018; 13:e0195277. [PMID: 29652886 PMCID: PMC5898730 DOI: 10.1371/journal.pone.0195277] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 03/19/2018] [Indexed: 01/23/2023] Open
Abstract
Single-molecule microscopy has become a widely used technique in (bio)physics and (bio)chemistry. A popular implementation is single-molecule Förster Resonance Energy Transfer (smFRET), for which total internal reflection fluorescence microscopy is frequently combined with camera-based detection of surface-immobilized molecules. Camera-based smFRET experiments generate large and complex datasets and several methods for video processing and analysis have been reported. As these algorithms often address similar aspects in video analysis, there is a growing need for standardized comparison. Here, we present a Matlab-based software (MASH-FRET) that allows for the simulation of camera-based smFRET videos, yielding standardized data sets suitable for benchmarking video processing algorithms. The software permits to vary parameters that are relevant in cameras-based smFRET, such as video quality, and the properties of the system under study. Experimental noise is modeled taking into account photon statistics and camera noise. Finally, we survey how video test sets should be designed to evaluate currently available data analysis strategies in camera-based sm fluorescence experiments. We complement our study by pre-optimizing and evaluating spot detection algorithms using our simulated video test sets.
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Affiliation(s)
- Richard Börner
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Danny Kowerko
- Department of Computer Science, Chemnitz University of Technology, Chemnitz, Germany
| | | | - Sebastian L. B. König
- Department of Chemistry, University of Zurich, Zurich, Switzerland
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Marc Ritter
- Department of Applied Computer and Biosciences, Mittweida University of Applied Sciences, Mittweida, Germany
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107
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Zheng W, Zerze GH, Borgia A, Mittal J, Schuler B, Best RB. Inferring properties of disordered chains from FRET transfer efficiencies. J Chem Phys 2018; 148:123329. [PMID: 29604882 PMCID: PMC5812746 DOI: 10.1063/1.5006954] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/10/2018] [Indexed: 11/15/2022] Open
Abstract
Förster resonance energy transfer (FRET) is a powerful tool for elucidating both structural and dynamic properties of unfolded or disordered biomolecules, especially in single-molecule experiments. However, the key observables, namely, the mean transfer efficiency and fluorescence lifetimes of the donor and acceptor chromophores, are averaged over a broad distribution of donor-acceptor distances. The inferred average properties of the ensemble therefore depend on the form of the model distribution chosen to describe the distance, as has been widely recognized. In addition, while the distribution for one type of polymer model may be appropriate for a chain under a given set of physico-chemical conditions, it may not be suitable for the same chain in a different environment so that even an apparently consistent application of the same model over all conditions may distort the apparent changes in chain dimensions with variation of temperature or solution composition. Here, we present an alternative and straightforward approach to determining ensemble properties from FRET data, in which the polymer scaling exponent is allowed to vary with solution conditions. In its simplest form, it requires either the mean FRET efficiency or fluorescence lifetime information. In order to test the accuracy of the method, we have utilized both synthetic FRET data from implicit and explicit solvent simulations for 30 different protein sequences, and experimental single-molecule FRET data for an intrinsically disordered and a denatured protein. In all cases, we find that the inferred radii of gyration are within 10% of the true values, thus providing higher accuracy than simpler polymer models. In addition, the scaling exponents obtained by our procedure are in good agreement with those determined directly from the molecular ensemble. Our approach can in principle be generalized to treating other ensemble-averaged functions of intramolecular distances from experimental data.
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Affiliation(s)
- Wenwei Zheng
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA
| | - Gül H Zerze
- Department of Chemical and Biomolecular Engineering, Bethlehem, Pennsylvania 18015, USA
| | - Alessandro Borgia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Jeetain Mittal
- Department of Chemical and Biomolecular Engineering, Bethlehem, Pennsylvania 18015, USA
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA
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108
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Reinartz I, Sinner C, Nettels D, Stucki-Buchli B, Stockmar F, Panek PT, Jacob CR, Nienhaus GU, Schuler B, Schug A. Simulation of FRET dyes allows quantitative comparison against experimental data. J Chem Phys 2018; 148:123321. [DOI: 10.1063/1.5010434] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Ines Reinartz
- Department of Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
- Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Claude Sinner
- Department of Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
- Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Brigitte Stucki-Buchli
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Florian Stockmar
- Institute of Applied Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
| | - Pawel T. Panek
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Gaußstraße 17, 38106 Braunschweig, Germany
| | - Christoph R. Jacob
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Gaußstraße 17, 38106 Braunschweig, Germany
| | - Gerd Ulrich Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
- HEiKA–Heidelberg Karlsruhe Research Partnership, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Institute of Nanotechnology and Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Alexander Schug
- Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- John von Neumann Institute for Computing, Jülich Supercomputing Centre, Forschungszentrum Jülich, 52425 Jülich, Germany
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109
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Yang J, Dear AJ, Michaels TCT, Dobson CM, Knowles TPJ, Wu S, Perrett S. Direct Observation of Oligomerization by Single Molecule Fluorescence Reveals a Multistep Aggregation Mechanism for the Yeast Prion Protein Ure2. J Am Chem Soc 2018; 140:2493-2503. [PMID: 29357227 PMCID: PMC5880511 DOI: 10.1021/jacs.7b10439] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
![]()
The self-assembly of polypeptides
into amyloid structures is associated
with a range of increasingly prevalent neurodegenerative diseases
as well as with a select set of functional processes in biology. The
phenomenon of self-assembly results in species with dramatically different
sizes, from small oligomers to large fibrils; however, the kinetic
relationship between these species is challenging to characterize.
In the case of prion aggregates, these structures can self-replicate
and act as infectious agents. Here we use single molecule spectroscopy
to obtain quantitative information on the oligomer populations formed
during aggregation of the yeast prion protein Ure2. Global analysis
of the aggregation kinetics reveals the molecular mechanism underlying
oligomer formation and depletion. Quantitative characterization indicates
that the majority of Ure2 oligomers are relatively short-lived, and
their rate of dissociation is much higher than their rate of conversion
into growing fibrils. We identify an initial metastable oligomer,
which can subsequently convert into a structurally distinct oligomer,
which in turn converts into growing fibrils. We also show that fragmentation
is responsible for the autocatalytic self-replication of Ure2 fibrils,
but that preformed fibrils do not promote oligomer formation, indicating
that secondary nucleation of the type observed for peptides and proteins
associated with neurodegenerative disease does not occur at a significant
rate for Ure2. These results establish a framework for elucidating
the temporal and causal relationship between oligomers and larger
fibrillar species in amyloid forming systems, and provide insights
into why functional amyloid systems are not toxic to their host organisms.
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Affiliation(s)
- Jie Yang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Alexander J Dear
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Thomas C T Michaels
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.,Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Christopher M Dobson
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Tuomas P J Knowles
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.,Cavendish Laboratory , J J Thomson Avenue, Cambridge CB3 1HE, United Kingdom
| | - Si Wu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Sarah Perrett
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , 15 Datun Road, Chaoyang District, Beijing 100101, China.,University of the Chinese Academy of Sciences , 19A Yuquan Road, Shijingshan District, Beijing 100049, China
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110
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Steffen FD, Sigel RKO, Börner R. An atomistic view on carbocyanine photophysics in the realm of RNA. Phys Chem Chem Phys 2018; 18:29045-29055. [PMID: 27783069 DOI: 10.1039/c6cp04277e] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Carbocyanine dyes have a long-standing tradition in fluorescence imaging and spectroscopy, due to their photostability and large spectral separation between individual dye species. Herein, we explore the versatility of cyanine dyes to probe the dynamics of nucleic acids and we report on the interrelation of fluorophores, RNA, and metal ions, namely K+ and Mg2+. Photophysical parameters including the fluorescence lifetime, quantum yield and dynamic anisotropy are monitored as a function of the nucleic acid composition, conformation, and metal ion abundance. Occasional excursions to a non-fluorescent cis-state hint at the remarkable sensitivity of carbocyanines to their local environment. Comparison of time-correlated single photon experiments with all-atom molecular dynamics simulations demonstrate that the propensity of photoisomerization is dictated by sterical constraints imposed on the fluorophore. Structural features in the vicinity of the dye play a crucial role in RNA recognition and have far-reaching implications on the mobility of the fluorescent probe. An atomic level description of the mutual interactions will ultimately benefit the quantitative interpretation of single-molecule FRET measurements on large RNA systems.
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Affiliation(s)
- Fabio D Steffen
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Roland K O Sigel
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Richard Börner
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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111
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Krainer G, Hartmann A, Anandamurugan A, Gracia P, Keller S, Schlierf M. Ultrafast Protein Folding in Membrane-Mimetic Environments. J Mol Biol 2018; 430:554-564. [DOI: 10.1016/j.jmb.2017.10.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/12/2017] [Accepted: 10/27/2017] [Indexed: 01/06/2023]
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112
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Lerner E, Cordes T, Ingargiol A, Alhadid Y, Chung S, Michalet X, Weiss S. Toward dynamic structural biology: Two decades of single-molecule Förster resonance energy transfer. Science 2018; 359:eaan1133. [PMID: 29348210 PMCID: PMC6200918 DOI: 10.1126/science.aan1133] [Citation(s) in RCA: 323] [Impact Index Per Article: 53.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Classical structural biology can only provide static snapshots of biomacromolecules. Single-molecule Förster resonance energy transfer (smFRET) paved the way for studying dynamics in macromolecular structures under biologically relevant conditions. Since its first implementation in 1996, smFRET experiments have confirmed previously hypothesized mechanisms and provided new insights into many fundamental biological processes, such as DNA maintenance and repair, transcription, translation, and membrane transport. We review 22 years of contributions of smFRET to our understanding of basic mechanisms in biochemistry, molecular biology, and structural biology. Additionally, building on current state-of-the-art implementations of smFRET, we highlight possible future directions for smFRET in applications such as biosensing, high-throughput screening, and molecular diagnostics.
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Affiliation(s)
- Eitan Lerner
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Thorben Cordes
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Antonino Ingargiol
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Yazan Alhadid
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - SangYoon Chung
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Xavier Michalet
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- Department of Physiology, University of California, Los Angeles, CA 90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA
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113
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Bhatia S, Krishnamoorthy G, Udgaonkar JB. Site-specific time-resolved FRET reveals local variations in the unfolding mechanism in an apparently two-state protein unfolding transition. Phys Chem Chem Phys 2018; 20:3216-3232. [DOI: 10.1039/c7cp06214a] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Using multi-site time-resolved FRET, it is shown that equilibrium unfolding of monellin is not only heterogeneous, but that the degree of non-cooperativity differs between the sole α-helix and different parts of the β-sheet.
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Affiliation(s)
- Sandhya Bhatia
- National Centre for Biological Sciences
- Tata Institute of Fundamental Research
- Bengaluru 560065
- India
| | | | - Jayant B. Udgaonkar
- National Centre for Biological Sciences
- Tata Institute of Fundamental Research
- Bengaluru 560065
- India
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114
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Holmstrom ED, Nesbitt DJ. Biophysical Insights from Temperature-Dependent Single-Molecule Förster Resonance Energy Transfer. Annu Rev Phys Chem 2017; 67:441-65. [PMID: 27215819 DOI: 10.1146/annurev-physchem-040215-112544] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Single-molecule fluorescence microscopy techniques can be used in combination with micrometer length-scale temperature control and Förster resonance energy transfer (FRET) in order to gain detailed information about fundamental biophysical phenomena. In particular, this combination of techniques has helped foster the development of remarkable quantitative tools for studying both time- and temperature-dependent structural kinetics of biopolymers. Over the past decade, multiple research efforts have successfully incorporated precise spatial and temporal control of temperature into single-molecule FRET (smFRET)-based experiments, which have uncovered critical thermodynamic information on a wide range of biological systems such as conformational dynamics of nucleic acids. This review provides an overview of various temperature-dependent smFRET approaches from our laboratory and others, highlighting efforts in which such methods have been successfully applied to studies of single-molecule nucleic acid folding.
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Affiliation(s)
- Erik D Holmstrom
- JILA, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309;
| | - David J Nesbitt
- JILA, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309;
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115
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Song J, Gomes GN, Shi T, Gradinaru CC, Chan HS. Conformational Heterogeneity and FRET Data Interpretation for Dimensions of Unfolded Proteins. Biophys J 2017; 113:1012-1024. [PMID: 28877485 DOI: 10.1016/j.bpj.2017.07.023] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/26/2017] [Accepted: 07/31/2017] [Indexed: 12/28/2022] Open
Abstract
A mathematico-physically valid formulation is required to infer properties of disordered protein conformations from single-molecule Förster resonance energy transfer (smFRET). Conformational dimensions inferred by conventional approaches that presume a homogeneous conformational ensemble can be unphysical. When all possible-heterogeneous as well as homogeneous-conformational distributions are taken into account without prejudgment, a single value of average transfer efficiency 〈E〉 between dyes at two chain ends is generally consistent with highly diverse, multiple values of the average radius of gyration 〈Rg〉. Here we utilize unbiased conformational statistics from a coarse-grained explicit-chain model to establish a general logical framework to quantify this fundamental ambiguity in smFRET inference. As an application, we address the long-standing controversy regarding the denaturant dependence of 〈Rg〉 of unfolded proteins, focusing on Protein L as an example. Conventional smFRET inference concluded that 〈Rg〉 of unfolded Protein L is highly sensitive to [GuHCl], but data from SAXS suggested a near-constant 〈Rg〉 irrespective of [GuHCl]. Strikingly, our analysis indicates that although the reported 〈E〉 values for Protein L at [GuHCl] = 1 and 7 M are very different at 0.75 and 0.45, respectively, the Bayesian Rg2 distributions consistent with these two 〈E〉 values overlap by as much as 75%. Our findings suggest, in general, that the smFRET-SAXS discrepancy regarding unfolded protein dimensions likely arise from highly heterogeneous conformational ensembles at low or zero denaturant, and that additional experimental probes are needed to ascertain the nature of this heterogeneity.
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Affiliation(s)
- Jianhui Song
- School of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China; Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Gregory-Neal Gomes
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada; Department of Physics, University of Toronto, Toronto, Ontario, Canada
| | - Tongfei Shi
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
| | - Claudiu C Gradinaru
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada; Department of Physics, University of Toronto, Toronto, Ontario, Canada
| | - Hue Sun Chan
- Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
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116
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Salvi N, Abyzov A, Blackledge M. Atomic resolution conformational dynamics of intrinsically disordered proteins from NMR spin relaxation. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2017; 102-103:43-60. [PMID: 29157493 DOI: 10.1016/j.pnmrs.2017.06.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 06/27/2017] [Accepted: 06/27/2017] [Indexed: 05/08/2023]
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental approaches for investigating the conformational behaviour of intrinsically disordered proteins (IDPs). IDPs represent a significant fraction of all proteomes, and, despite their importance for understanding fundamental biological processes, the molecular basis of their activity still remains largely unknown. The functional mechanisms exploited by IDPs in their interactions with other biomolecules are defined by their intrinsic dynamic modes and associated timescales, justifying the considerable interest over recent years in the development of technologies adapted to measure and describe this behaviour. NMR spin relaxation delivers information-rich, site-specific data reporting on conformational fluctuations occurring throughout the molecule. Here we review recent progress in the use of 15N relaxation to identify local backbone dynamics and long-range chain-like motions in unfolded proteins.
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Affiliation(s)
- Nicola Salvi
- Institut de Biologie Structurale (IBS), CEA, CNRS, University Grenoble Alpes, Grenoble 38044, France
| | - Anton Abyzov
- Institut de Biologie Structurale (IBS), CEA, CNRS, University Grenoble Alpes, Grenoble 38044, France
| | - Martin Blackledge
- Institut de Biologie Structurale (IBS), CEA, CNRS, University Grenoble Alpes, Grenoble 38044, France.
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117
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Zosel F, Haenni D, Soranno A, Nettels D, Schuler B. Combining short- and long-range fluorescence reporters with simulations to explore the intramolecular dynamics of an intrinsically disordered protein. J Chem Phys 2017; 147:152708. [DOI: 10.1063/1.4992800] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Affiliation(s)
- Franziska Zosel
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Dominik Haenni
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
- Center for Microscopy and Image Analysis, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Andrea Soranno
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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118
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Biophysical Aspects of Alzheimer's Disease: Implications for Pharmaceutical Sciences : Theme: Drug Discovery, Development and Delivery in Alzheimer's Disease Guest Editor: Davide Brambilla. Pharm Res 2017; 34:2628-2636. [PMID: 28963701 DOI: 10.1007/s11095-017-2266-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 09/15/2017] [Indexed: 10/18/2022]
Abstract
An increasing amount of findings suggests that the aggregation of soluble peptides and proteins into amyloid fibrils is a relevant upstream process in the complex cascade of events leading to the pathology of Alzheimer's disease and several other neurodegenerative disorders. Nevertheless, several aspects of the correlation between the aggregation process and the onset and development of the pathology remain largely elusive. In this context, biophysical and biochemical studies in test tubes have proven extremely powerful in providing quantitative information about the structure and the reactivity of amyloids at the molecular level. In this review we use selected recent examples to illustrate the importance of such biophysical research to complement phenomenological studies based on cellular and molecular biology, and we discuss the implications for pharmaceutical applications associated with Alzheimer's disease and other neurodegenerative disorders in both academic and industrial contexts.
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119
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Rahamim G, Amir D, Haas E. Simultaneous Determination of Two Subdomain Folding Rates Using the "Transfer-Quench" Method. Biophys J 2017; 112:1786-1796. [PMID: 28494950 DOI: 10.1016/j.bpj.2017.01.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 12/21/2016] [Accepted: 01/06/2017] [Indexed: 11/29/2022] Open
Abstract
The investigation of the mechanism of protein folding is complicated by the context dependence of the rates of intramolecular contact formation. Methods based on site-specific labeling and ultrafast spectroscopic detection of fluorescence signals were developed for monitoring the rates of individual subdomain folding transitions in situ, in the context of the whole molecule. However, each site-specific labeling modification might affect rates of folding of near-neighbor structural elements, and thus limit the ability to resolve fine differences in rates of folding of these elements. Therefore, it is highly desirable to be able to study the rates of folding of two or more neighboring subdomain structures using a single mutant to facilitate resolution of the order and interdependence of such steps. Here, we report the development of the "Transfer-Quench" method for measuring the rate of formation of two structural elements using a single triple-labeled mutant. This method is based on Förster resonance energy transfer combined with fluorescence quenching. We placed the donor and acceptor at the loop ends, and a quencher at an α-helical element involved in the node forming the loop. The folding of the triple-labeled mutant is monitored by the acceptor emission. The formation of nonlocal contact (loop closure) increases the time-dependent acceptor emission, while the closure of the labeled helix turn reduces this emission. The method was applied in a study of the folding mechanism of the common model protein, the B domain of staphylococcal protein A. Only natural amino acids were used as probes, and thus possible structural perturbations were minimized. Tyr and Trp residues served as donor and acceptor at the ends of a long loop between helices I and II, and a Cys residue as a quencher for the acceptor. We found that the closure of the loop (segment 14-33) occurs with the same rate constant as the nucleation of helix HII (segment 33-29), in line with the nucleation-condensation model.
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Affiliation(s)
- Gil Rahamim
- The Goodman Faculty of Life Sciences Bar Ilan University, Ramat Gan, Israel
| | - Dan Amir
- The Goodman Faculty of Life Sciences Bar Ilan University, Ramat Gan, Israel
| | - Elisha Haas
- The Goodman Faculty of Life Sciences Bar Ilan University, Ramat Gan, Israel.
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120
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Plitzko JM, Schuler B, Selenko P. Structural Biology outside the box-inside the cell. Curr Opin Struct Biol 2017; 46:110-121. [PMID: 28735108 DOI: 10.1016/j.sbi.2017.06.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 06/17/2017] [Accepted: 06/23/2017] [Indexed: 01/11/2023]
Abstract
Recent developments in cellular cryo-electron tomography, in-cell single-molecule Förster resonance energy transfer-spectroscopy, nuclear magnetic resonance-spectroscopy and electron paramagnetic resonance-spectroscopy delivered unprecedented insights into the inner workings of cells. Here, we review complementary aspects of these methods and provide an outlook toward joint applications in the future.
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Affiliation(s)
- Jürgen M Plitzko
- Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, D-82152 Martinsried, Germany
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Philipp Selenko
- Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Laboratory, Robert-Roessle Strasse 10, D-13125 Berlin, Germany.
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121
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Krainer G, Gracia P, Frotscher E, Hartmann A, Gröger P, Keller S, Schlierf M. Slow Interconversion in a Heterogeneous Unfolded-State Ensemble of Outer-Membrane Phospholipase A. Biophys J 2017. [PMID: 28629619 DOI: 10.1016/j.bpj.2017.05.037] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Structural and dynamic investigations of unfolded proteins are important for understanding protein-folding mechanisms as well as the interactions of unfolded polypeptide chains with other cell components. In the case of outer-membrane proteins (OMPs), unfolded-state properties are of particular physiological relevance, because these proteins remain unfolded for extended periods of time during their biogenesis and rely on interactions with binding partners to support proper folding. Using a combination of ensemble and single-molecule spectroscopy, we have scrutinized the unfolded state of outer-membrane phospholipase A (OmpLA) to provide a detailed view of its structural dynamics on timescales from nanoseconds to milliseconds. We find that even under strongly denaturing conditions and in the absence of residual secondary structure, OmpLA populates an ensemble of slowly (>100 ms) interconverting and conformationally heterogeneous unfolded states that lack the fast chain-reconfiguration motions expected for an unstructured, fully unfolded chain. The drastically slowed sampling of potentially folding-competent states, as compared with a random-coil polypeptide, may contribute to the slow in vitro folding kinetics observed for many OMPs. In vivo, however, slow intramolecular long-range dynamics might be advantageous for entropically favored binding of unfolded OMPs to chaperones and, by facilitating conformational selection after release from chaperones, for preserving binding-competent conformations before insertion into the outer membrane.
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Affiliation(s)
- Georg Krainer
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany; Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Pablo Gracia
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Erik Frotscher
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Andreas Hartmann
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Philip Gröger
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Sandro Keller
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany.
| | - Michael Schlierf
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany.
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122
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Abstract
Heat shock protein 90 (Hsp90) is a molecular chaperone that is involved in the activation of disparate client proteins. This implicates Hsp90 in diverse biological processes that require a variety of co-ordinated regulatory mechanisms to control its activity. Perhaps the most important regulator is heat shock factor 1 (HSF1), which is primarily responsible for upregulating Hsp90 by binding heat shock elements (HSEs) within Hsp90 promoters. HSF1 is itself subject to a variety of regulatory processes and can directly respond to stress. HSF1 also interacts with a variety of transcriptional factors that help integrate biological signals, which in turn regulate Hsp90 appropriately. Because of the diverse clientele of Hsp90 a whole variety of co-chaperones also regulate its activity and some are directly responsible for delivery of client protein. Consequently, co-chaperones themselves, like Hsp90, are also subject to regulatory mechanisms such as post translational modification. This review, looks at the many different levels by which Hsp90 activity is ultimately regulated.
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123
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Zijlstra N, Dingfelder F, Wunderlich B, Zosel F, Benke S, Nettels D, Schuler B. Rapid Microfluidic Dilution for Single-Molecule Spectroscopy of Low-Affinity Biomolecular Complexes. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201702439] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Niels Zijlstra
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Fabian Dingfelder
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Bengt Wunderlich
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Franziska Zosel
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Stephan Benke
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Daniel Nettels
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Benjamin Schuler
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
- Department of Physics; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
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124
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Zijlstra N, Dingfelder F, Wunderlich B, Zosel F, Benke S, Nettels D, Schuler B. Rapid Microfluidic Dilution for Single-Molecule Spectroscopy of Low-Affinity Biomolecular Complexes. Angew Chem Int Ed Engl 2017; 56:7126-7129. [DOI: 10.1002/anie.201702439] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 04/11/2017] [Indexed: 02/04/2023]
Affiliation(s)
- Niels Zijlstra
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Fabian Dingfelder
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Bengt Wunderlich
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Franziska Zosel
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Stephan Benke
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Daniel Nettels
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Benjamin Schuler
- Department of Biochemistry; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
- Department of Physics; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
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125
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Dingfelder F, Wunderlich B, Benke S, Zosel F, Zijlstra N, Nettels D, Schuler B. Rapid Microfluidic Double-Jump Mixing Device for Single-Molecule Spectroscopy. J Am Chem Soc 2017; 139:6062-6065. [DOI: 10.1021/jacs.7b02357] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Fabian Dingfelder
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Bengt Wunderlich
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Stephan Benke
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Franziska Zosel
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Niels Zijlstra
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Daniel Nettels
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Benjamin Schuler
- Department
of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
- Department
of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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126
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Benke S, Nettels D, Hofmann H, Schuler B. Quantifying kinetics from time series of single-molecule Förster resonance energy transfer efficiency histograms. NANOTECHNOLOGY 2017; 28:114002. [PMID: 28103588 DOI: 10.1088/1361-6528/aa5abd] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Single-molecule fluorescence spectroscopy is a powerful approach for probing biomolecular structure and dynamics, including protein folding. For the investigation of nonequilibrium kinetics, Förster resonance energy transfer combined with confocal multiparameter detection has proven particularly versatile, owing to the large number of observables and the broad range of accessible timescales, especially in combination with rapid microfluidic mixing. However, a comprehensive kinetic analysis of the resulting time series of transfer efficiency histograms and complementary observables can be challenging owing to the complexity of the data. Here we present and compare three different methods for the analysis of such kinetic data: singular value decomposition, multivariate curve resolution with alternating least square fitting, and model-based peak fitting, where an explicit model of both the transfer efficiency histogram of each species and the kinetic mechanism of the process is employed. While each of these methods has its merits for specific applications, we conclude that model-based peak fitting is most suitable for a quantitative analysis and comparison of kinetic mechanisms.
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Affiliation(s)
- Stephan Benke
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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127
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Computational and theoretical advances in studies of intrinsically disordered proteins. Curr Opin Struct Biol 2017; 42:147-154. [PMID: 28259050 DOI: 10.1016/j.sbi.2017.01.006] [Citation(s) in RCA: 156] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 01/16/2017] [Accepted: 01/21/2017] [Indexed: 01/08/2023]
Abstract
Intrinsically disordered proteins (IDPs) are increasingly realized to play diverse biological roles, ranging from molecular signaling to the formation of membraneless organelles. Their high degree of disorder makes them more challenging to study using the techniques of conventional structural biology, because any observable will be averaged over a heterogeneous ensemble of structures. Molecular simulations and theory are therefore a natural complement to experiment for studying the structure, dynamics and function of IDPs. The diverse time and length scales relevant to the roles played by IDPs require flexibility in the techniques applied. Here, I summarize some of the developments in simulation and theory in recent years, which have been driven by the desire to better capture IDP properties at different time- and length-scales. I also provide an outlook for how methods can be improved in the future and emerging problems which may be addressed by theory and simulation.
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128
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Pancsa R, Raimondi D, Cilia E, Vranken WF. Early Folding Events, Local Interactions, and Conservation of Protein Backbone Rigidity. Biophys J 2017; 110:572-583. [PMID: 26840723 DOI: 10.1016/j.bpj.2015.12.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 12/21/2015] [Accepted: 12/29/2015] [Indexed: 01/20/2023] Open
Abstract
Protein folding is in its early stages largely determined by the protein sequence and complex local interactions between amino acids, resulting in lower energy conformations that provide the context for further folding into the native state. We compiled a comprehensive data set of early folding residues based on pulsed labeling hydrogen deuterium exchange experiments. These early folding residues have corresponding higher backbone rigidity as predicted by DynaMine from sequence, an effect also present when accounting for the secondary structures in the folded protein. We then show that the amino acids involved in early folding events are not more conserved than others, but rather, early folding fragments and the secondary structure elements they are part of show a clear trend toward conserving a rigid backbone. We therefore propose that backbone rigidity is a fundamental physical feature conserved by proteins that can provide important insights into their folding mechanisms and stability.
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Affiliation(s)
- Rita Pancsa
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Daniele Raimondi
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Elisa Cilia
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Wim F Vranken
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.
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129
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Edwards DT, Perkins TT. Optimizing force spectroscopy by modifying commercial cantilevers: Improved stability, precision, and temporal resolution. J Struct Biol 2017; 197:13-25. [DOI: 10.1016/j.jsb.2016.01.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/13/2016] [Accepted: 01/18/2016] [Indexed: 11/24/2022]
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130
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Single-molecule force spectroscopy on polyproteins and receptor–ligand complexes: The current toolbox. J Struct Biol 2017; 197:3-12. [DOI: 10.1016/j.jsb.2016.02.011] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 02/08/2016] [Accepted: 02/09/2016] [Indexed: 11/21/2022]
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131
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Kempe D, Cerminara M, Poblete S, Schöne A, Gabba M, Fitter J. Single-Molecule FRET Measurements in Additive-Enriched Aqueous Solutions. Anal Chem 2016; 89:694-702. [PMID: 27966879 DOI: 10.1021/acs.analchem.6b03147] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The addition of high amounts of chemical denaturants, salts, viscosity enhancers or macro-molecular crowding agents has an impact on the physical properties of buffer solutions. Among others, the (microscopic) viscosity, the refractive index, the dielectric constant, and the ionic strength can be affected. Here, we systematically evaluate the importance of solvent characteristics with respect to single-molecule FRET (smFRET) data. First, we present a confocal based method for the determination of fluorescence quantum yields to facilitate a fast characterization of smFRET-samples at sub-nM-concentrations. As a case study, we analyze smFRET data of structurally rigid, double-stranded DNA-oligonucleotides in aqueous buffer and in buffers with specific amounts of glycerol, guanidine hydrochloride (GdnHCl), and sodium chloride (NaCl) added. We show that the calculation of interdye distances, without taking into account solvent-induced spectral and photophysical changes of the labels, leads to deviations of up to 4 Å from the real interdye distances. Additionally, we demonstrate that electrostatic dye-dye repulsions are negligible for the interdye distance regime considered here (>50 Å). Finally, we use our approach to validate the further compaction of the already unfolded state of phosphoglycerate kinase (PGK) with decreasing denaturant concentrations, a mechanism known as coil-globule transition.
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Affiliation(s)
- Daryan Kempe
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
| | | | | | | | | | - Jörg Fitter
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
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132
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Thommen M, Holtkamp W, Rodnina MV. Co-translational protein folding: progress and methods. Curr Opin Struct Biol 2016; 42:83-89. [PMID: 27940242 DOI: 10.1016/j.sbi.2016.11.020] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 11/22/2016] [Indexed: 11/19/2022]
Abstract
Proteins are synthesized as linear polymers and have to fold into their native structure to fulfil various functions in the cell. Folding can start co-translationally when the emerging peptide is still attached to the ribosome and is guided by the environment of the polypeptide exit tunnel and the kinetics of translation. Major questions are: When does co-translational folding begin? What is the role of the ribosome in guiding the nascent peptide towards its native structure? How does translation elongation kinetics modulate protein folding? Here we suggest how novel structural and biophysical approaches can help to probe the interplay between the ribosome and the emerging peptide and present future challenges in understanding co-translational folding.
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Affiliation(s)
- Michael Thommen
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen 37077, Germany
| | - Wolf Holtkamp
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen 37077, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen 37077, Germany.
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133
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Sasmal DK, Pulido LE, Kasal S, Huang J. Single-molecule fluorescence resonance energy transfer in molecular biology. NANOSCALE 2016; 8:19928-19944. [PMID: 27883140 PMCID: PMC5145784 DOI: 10.1039/c6nr06794h] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Single-molecule fluorescence resonance energy transfer (smFRET) is a powerful technique for studying the conformation dynamics and interactions of individual biomolecules. In this review, we describe the concept and principle of smFRET, illustrate general instrumentation and microscopy settings for experiments, and discuss the methods and algorithms for data analysis. Subsequently, we review applications of smFRET in protein conformational changes, ion channel open-close properties, receptor-ligand interactions, nucleic acid structure regulation, vesicle fusion, and force induced conformational dynamics. Finally, we discuss the main limitations of smFRET in molecular biology.
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Affiliation(s)
- Dibyendu K Sasmal
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Laura E Pulido
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Shan Kasal
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Jun Huang
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
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134
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Dimura M, Peulen TO, Hanke CA, Prakash A, Gohlke H, Seidel CA. Quantitative FRET studies and integrative modeling unravel the structure and dynamics of biomolecular systems. Curr Opin Struct Biol 2016; 40:163-185. [PMID: 27939973 DOI: 10.1016/j.sbi.2016.11.012] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 11/11/2016] [Accepted: 11/11/2016] [Indexed: 01/11/2023]
Abstract
Förster Resonance Energy Transfer (FRET) combined with single-molecule spectroscopy probes macromolecular structure and dynamics and identifies coexisting conformational states. We review recent methodological developments in integrative structural modeling by satisfying spatial restraints on networks of FRET pairs (hybrid-FRET). We discuss procedures to incorporate prior structural knowledge and to obtain optimal distance networks. Finally, a workflow for hybrid-FRET is presented that automates integrative structural modeling and experiment planning to put hybrid-FRET on rails. To test this workflow, we simulate realistic single-molecule experiments and resolve three protein conformers, exchanging at 30μs and 10ms, with accuracies of 1-3Å RMSD versus the target structure. Incorporation of data from other spectroscopies and imaging is also discussed.
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Affiliation(s)
- Mykola Dimura
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Thomas O Peulen
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Christian A Hanke
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Aiswaria Prakash
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Claus Am Seidel
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany.
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135
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Mori T, Saito S. Molecular Mechanism Behind the Fast Folding/Unfolding Transitions of Villin Headpiece Subdomain: Hierarchy and Heterogeneity. J Phys Chem B 2016; 120:11683-11691. [DOI: 10.1021/acs.jpcb.6b08066] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Toshifumi Mori
- Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki, Aichi 444-8585, Japan
| | - Shinji Saito
- Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki, Aichi 444-8585, Japan
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136
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Malhotra P, Udgaonkar JB. How cooperative are protein folding and unfolding transitions? Protein Sci 2016; 25:1924-1941. [PMID: 27522064 PMCID: PMC5079258 DOI: 10.1002/pro.3015] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 08/09/2016] [Accepted: 08/09/2016] [Indexed: 11/12/2022]
Abstract
A thermodynamically and kinetically simple picture of protein folding envisages only two states, native (N) and unfolded (U), separated by a single activation free energy barrier, and interconverting by cooperative two-state transitions. The folding/unfolding transitions of many proteins occur, however, in multiple discrete steps associated with the formation of intermediates, which is indicative of reduced cooperativity. Furthermore, much advancement in experimental and computational approaches has demonstrated entirely non-cooperative (gradual) transitions via a continuum of states and a multitude of small energetic barriers between the N and U states of some proteins. These findings have been instrumental towards providing a structural rationale for cooperative versus noncooperative transitions, based on the coupling between interaction networks in proteins. The cooperativity inherent in a folding/unfolding reaction appears to be context dependent, and can be tuned via experimental conditions which change the stabilities of N and U. The evolution of cooperativity in protein folding transitions is linked closely to the evolution of function as well as the aggregation propensity of the protein. A large activation energy barrier in a fully cooperative transition can provide the kinetic control required to prevent the accumulation of partially unfolded forms, which may promote aggregation. Nevertheless, increasing evidence for barrier-less "downhill" folding, as well as for continuous "uphill" unfolding transitions, indicate that gradual non-cooperative processes may be ubiquitous features on the free energy landscape of protein folding.
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Affiliation(s)
- Pooja Malhotra
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, 560065, India
| | - Jayant B Udgaonkar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, 560065, India.
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137
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Chingin K, Barylyuk K, Chen H. On the preservation of non-covalent protein complexes during electrospray ionization. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0377. [PMID: 27644969 PMCID: PMC5031642 DOI: 10.1098/rsta.2015.0377] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/13/2016] [Indexed: 06/06/2023]
Abstract
The application range of electrospray ionization mass spectrometry for the quantitative determination of stoichiometries and binding constants for non-covalent protein complexes is broadly discussed. The underlying fundamental question is whether or not the original molecular equilibrium can be preserved during the ionization process and be revealed by subsequent mass spectrometry analysis. Here, we take a new look at this question by discussing recent studies in droplet chemistry.This article is part of the themed issue 'Quantitative mass spectrometry'.
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Affiliation(s)
- Konstantin Chingin
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Guanglan Road 418, Nanchang, Jiangxi 330013, People's Republic of China
| | - Konstantin Barylyuk
- Department of Biochemistry, University of Cambridge, Hopkins Building, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Huanwen Chen
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Guanglan Road 418, Nanchang, Jiangxi 330013, People's Republic of China
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138
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The Power of Force: Insights into the Protein Folding Process Using Single-Molecule Force Spectroscopy. J Mol Biol 2016; 428:4245-4257. [PMID: 27639437 DOI: 10.1016/j.jmb.2016.09.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/07/2016] [Accepted: 09/07/2016] [Indexed: 01/03/2023]
Abstract
One of the major challenges in modern biophysics is observing and understanding conformational changes during complex molecular processes, from the fundamental protein folding to the function of molecular machines. Single-molecule techniques have been one of the major driving forces of the huge progress attained in the last few years. Recent advances in resolution of the experimental setups, aided by theoretical developments and molecular dynamics simulations, have revealed a much higher degree of complexity inside these molecular processes than previously reported using traditional ensemble measurements. This review sums up the evolution of these developments and gives an outlook on prospective discoveries.
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139
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Borgia A, Zheng W, Buholzer K, Borgia MB, Schüler A, Hofmann H, Soranno A, Nettels D, Gast K, Grishaev A, Best RB, Schuler B. Consistent View of Polypeptide Chain Expansion in Chemical Denaturants from Multiple Experimental Methods. J Am Chem Soc 2016; 138:11714-26. [PMID: 27583570 PMCID: PMC5597961 DOI: 10.1021/jacs.6b05917] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
There has been a long-standing controversy regarding the effect of chemical denaturants on the dimensions of unfolded and intrinsically disordered proteins: A wide range of experimental techniques suggest that polypeptide chains expand with increasing denaturant concentration, but several studies using small-angle X-ray scattering (SAXS) have reported no such increase of the radius of gyration (Rg). This inconsistency challenges our current understanding of the mechanism of chemical denaturants, which are widely employed to investigate protein folding and stability. Here, we use a combination of single-molecule Förster resonance energy transfer (FRET), SAXS, dynamic light scattering (DLS), and two-focus fluorescence correlation spectroscopy (2f-FCS) to characterize the denaturant dependence of the unfolded state of the spectrin domain R17 and the intrinsically disordered protein ACTR in two different denaturants. Standard analysis of the primary data clearly indicates an expansion of the unfolded state with increasing denaturant concentration irrespective of the protein, denaturant, or experimental method used. This is the first case in which SAXS and FRET have yielded even qualitatively consistent results regarding expansion in denaturant when applied to the same proteins. To more directly illustrate this self-consistency, we used both SAXS and FRET data in a Bayesian procedure to refine structural ensembles representative of the observed unfolded state. This analysis demonstrates that both of these experimental probes are compatible with a common ensemble of protein configurations for each denaturant concentration. Furthermore, the resulting ensembles reproduce the trend of increasing hydrodynamic radius with denaturant concentration obtained by 2f-FCS and DLS. We were thus able to reconcile the results from all four experimental techniques quantitatively, to obtain a comprehensive structural picture of denaturant-induced unfolded state expansion, and to identify the most likely sources of earlier discrepancies.
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Affiliation(s)
- Alessandro Borgia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Wenwei Zheng
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda 20892-0520
| | - Karin Buholzer
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Madeleine B. Borgia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Anja Schüler
- Physical Biochemistry, University of Potsdam, 14476 Potsdam, Germany
| | - Hagen Hofmann
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Andrea Soranno
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Klaus Gast
- Physical Biochemistry, University of Potsdam, 14476 Potsdam, Germany
| | - Alexander Grishaev
- National Institute of Standards and Technology and the Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, MD 20850
| | - Robert B. Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda 20892-0520
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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140
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Aznauryan M, Delgado L, Soranno A, Nettels D, Huang JR, Labhardt AM, Grzesiek S, Schuler B. Comprehensive structural and dynamical view of an unfolded protein from the combination of single-molecule FRET, NMR, and SAXS. Proc Natl Acad Sci U S A 2016; 113:E5389-98. [PMID: 27566405 PMCID: PMC5027429 DOI: 10.1073/pnas.1607193113] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The properties of unfolded proteins are essential both for the mechanisms of protein folding and for the function of the large group of intrinsically disordered proteins. However, the detailed structural and dynamical characterization of these highly dynamic and conformationally heterogeneous ensembles has remained challenging. Here we combine and compare three of the leading techniques for the investigation of unfolded proteins, NMR spectroscopy (NMR), small-angle X-ray scattering (SAXS), and single-molecule Förster resonance energy transfer (FRET), with the goal of quantitatively testing their consistency and complementarity and for obtaining a comprehensive view of the unfolded-state ensemble. Using unfolded ubiquitin as a test case, we find that its average dimensions derived from FRET and from structural ensembles calculated using the program X-PLOR-NIH based on NMR and SAXS restraints agree remarkably well; even the shapes of the underlying intramolecular distance distributions are in good agreement, attesting to the reliability of the approaches. The NMR-based results provide a highly sensitive way of quantifying residual structure in the unfolded state. FRET-based nanosecond fluorescence correlation spectroscopy allows long-range distances and chain dynamics to be probed in a time range inaccessible by NMR. The combined techniques thus provide a way of optimally using the complementarity of the available methods for a quantitative structural and dynamical description of unfolded proteins both at the global and the local level.
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Affiliation(s)
- Mikayel Aznauryan
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | | | - Andrea Soranno
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Jie-Rong Huang
- Institute of Biochemistry and Molecular Biology, National Yang Ming University, Taipei City 112, Taiwan
| | | | | | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland; Department of Physics, University of Zurich, 8057 Zurich, Switzerland
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141
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Saito M, Kamonprasertsuk S, Suzuki S, Nanatani K, Oikawa H, Kushiro K, Takai M, Chen PT, Chen EHL, Chen RPY, Takahashi S. Significant Heterogeneity and Slow Dynamics of the Unfolded Ubiquitin Detected by the Line Confocal Method of Single-Molecule Fluorescence Spectroscopy. J Phys Chem B 2016; 120:8818-29. [DOI: 10.1021/acs.jpcb.6b05481] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Masataka Saito
- Institute
for Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School and Faculty of Science, Tohoku University, Sendai 980-8578, Japan
| | - Supawich Kamonprasertsuk
- Institute
for Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School and Faculty of Science, Tohoku University, Sendai 980-8578, Japan
| | - Satomi Suzuki
- Laboratory
of Applied Microbiology, Department of Microbial Biotechnology, Graduate
School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
| | - Kei Nanatani
- Department
of Microbial Resources, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
| | - Hiroyuki Oikawa
- Institute
for Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School and Faculty of Science, Tohoku University, Sendai 980-8578, Japan
| | - Keiichiro Kushiro
- Department
of Bioengineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Madoka Takai
- Department
of Bioengineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Po-ting Chen
- Institute
of Biological Chemistry, Academia Sinica, No. 128, Sec. 2, Academia Rd, Nankang, Taipei 11529, Taiwan
- Institute
of Biochemical Sciences, National Taiwan University, No. 1. Sec.
4, Roosevelt Rd, Taipei 10617, Taiwan
| | - Eric H.-L. Chen
- Institute
of Biological Chemistry, Academia Sinica, No. 128, Sec. 2, Academia Rd, Nankang, Taipei 11529, Taiwan
| | - Rita P.-Y. Chen
- Institute
of Biological Chemistry, Academia Sinica, No. 128, Sec. 2, Academia Rd, Nankang, Taipei 11529, Taiwan
- Institute
of Biochemical Sciences, National Taiwan University, No. 1. Sec.
4, Roosevelt Rd, Taipei 10617, Taiwan
| | - Satoshi Takahashi
- Institute
for Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School and Faculty of Science, Tohoku University, Sendai 980-8578, Japan
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142
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Schulze A, Beliu G, Helmerich DA, Schubert J, Pearl LH, Prodromou C, Neuweiler H. Cooperation of local motions in the Hsp90 molecular chaperone ATPase mechanism. Nat Chem Biol 2016; 12:628-35. [PMID: 27322067 PMCID: PMC4955915 DOI: 10.1038/nchembio.2111] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 04/14/2016] [Indexed: 11/08/2022]
Abstract
The Hsp90 chaperone is a central node of protein homeostasis, activating many diverse client proteins. Hsp90 functions as a molecular clamp that closes and opens in response to the binding and hydrolysis of ATP. Crystallographic studies have defined distinct conformational states of the mechanistic core, implying structural changes that have not yet been observed in solution. Here we engineered one-nanometer fluorescence probes based on photoinduced electron transfer into the yeast Hsp90 to observe these motions. We found that the ATPase activity of the chaperone was reflected in the kinetics of specific structural rearrangements at remote positions that acted cooperatively. Nanosecond single-molecule fluorescence fluctuation analysis uncovered that critical structural elements that undergo rearrangement were mobile on a sub-millisecond time scale. We identified a two-step mechanism for lid closure over the nucleotide-binding pocket. The activating co-chaperone Aha1 mobilized the lid of apo Hsp90, suggesting an early role in the catalytic cycle.
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Affiliation(s)
- Andrea Schulze
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Gerti Beliu
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Dominic A. Helmerich
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Jonathan Schubert
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Laurence H. Pearl
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, United Kingdom
| | - Chrisostomos Prodromou
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, United Kingdom
| | - Hannes Neuweiler
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
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143
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The Differential Response of Proteins to Macromolecular Crowding. PLoS Comput Biol 2016; 12:e1005040. [PMID: 27471851 PMCID: PMC4966950 DOI: 10.1371/journal.pcbi.1005040] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 06/27/2016] [Indexed: 12/02/2022] Open
Abstract
The habitat in which proteins exert their function contains up to 400 g/L of macromolecules, most of which are proteins. The repercussions of this dense environment on protein behavior are often overlooked or addressed using synthetic agents such as poly(ethylene glycol), whose ability to mimic protein crowders has not been demonstrated. Here we performed a comprehensive atomistic molecular dynamic analysis of the effect of protein crowders on the structure and dynamics of three proteins, namely an intrinsically disordered protein (ACTR), a molten globule conformation (NCBD), and a one-fold structure (IRF-3) protein. We found that crowding does not stabilize the native compact structure, and, in fact, often prevents structural collapse. Poly(ethylene glycol) PEG500 failed to reproduce many aspects of the physiologically-relevant protein crowders, thus indicating its unsuitability to mimic the cell interior. Instead, the impact of protein crowding on the structure and dynamics of a protein depends on its degree of disorder and results from two competing effects: the excluded volume, which favors compact states, and quinary interactions, which favor extended conformers. Such a viscous environment slows down protein flexibility and restricts the conformational landscape, often biasing it towards bioactive conformations but hindering biologically relevant protein-protein contacts. Overall, the protein crowders used here act as unspecific chaperons that modulate the protein conformational space, thus having relevant consequences for disordered proteins. Most in vitro and in silico biophysical experiments generally study proteins in an isolated environment, overlooking that their natural environment—the cell cytoplasm—is a solution that is highly populated by proteins. To address this knowledge gap, here we explored how a crowded environment alters the conformational sampling of three proteins, each with a different degree of disorder and flexibility. We simulated a crowded system composed by the three proteins and reaching a cell-like concentration and compared the protein behavior observed with that induced by PEG500, a synthetic crowding agent. Despite some similarities between the environments, protein crowders showed a number of characteristics that raise concerns about the use of diluted solutions or synthetic agents when studying protein behavior.
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144
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Laine RF, Kaminski Schierle GS, van de Linde S, Kaminski CF. From single-molecule spectroscopy to super-resolution imaging of the neuron: a review. Methods Appl Fluoresc 2016; 4:022004. [PMID: 28809165 PMCID: PMC5390958 DOI: 10.1088/2050-6120/4/2/022004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 05/09/2016] [Accepted: 05/19/2016] [Indexed: 12/03/2022]
Abstract
For more than 20 years, single-molecule spectroscopy has been providing invaluable insights into nature at the molecular level. The field has received a powerful boost with the development of the technique into super-resolution imaging methods, ca. 10 years ago, which overcome the limitations imposed by optical diffraction. Today, single molecule super-resolution imaging is routinely used in the study of macromolecular function and structure in the cell. Concomitantly, computational methods have been developed that provide information on numbers and positions of molecules at the nanometer-scale. In this overview, we outline the technical developments that have led to the emergence of localization microscopy techniques from single-molecule spectroscopy. We then provide a comprehensive review on the application of the technique in the field of neuroscience research.
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Affiliation(s)
- Romain F Laine
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
| | - Gabriele S Kaminski Schierle
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
| | - Sebastian van de Linde
- Department of Biotechnology and Biophysics, Julius-Maximilians-University, Am Hubland, D-97074 Würzburg, Germany
| | - Clemens F Kaminski
- Laser Analytics Group, Department of Chemical Engineering and Biotechnology, Cambridge University, Pembroke Street, Cambridge, CB2 3RA, UK
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145
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Wei G, Xi W, Nussinov R, Ma B. Protein Ensembles: How Does Nature Harness Thermodynamic Fluctuations for Life? The Diverse Functional Roles of Conformational Ensembles in the Cell. Chem Rev 2016; 116:6516-51. [PMID: 26807783 PMCID: PMC6407618 DOI: 10.1021/acs.chemrev.5b00562] [Citation(s) in RCA: 253] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
All soluble proteins populate conformational ensembles that together constitute the native state. Their fluctuations in water are intrinsic thermodynamic phenomena, and the distributions of the states on the energy landscape are determined by statistical thermodynamics; however, they are optimized to perform their biological functions. In this review we briefly describe advances in free energy landscape studies of protein conformational ensembles. Experimental (nuclear magnetic resonance, small-angle X-ray scattering, single-molecule spectroscopy, and cryo-electron microscopy) and computational (replica-exchange molecular dynamics, metadynamics, and Markov state models) approaches have made great progress in recent years. These address the challenging characterization of the highly flexible and heterogeneous protein ensembles. We focus on structural aspects of protein conformational distributions, from collective motions of single- and multi-domain proteins, intrinsically disordered proteins, to multiprotein complexes. Importantly, we highlight recent studies that illustrate functional adjustment of protein conformational ensembles in the crowded cellular environment. We center on the role of the ensemble in recognition of small- and macro-molecules (protein and RNA/DNA) and emphasize emerging concepts of protein dynamics in enzyme catalysis. Overall, protein ensembles link fundamental physicochemical principles and protein behavior and the cellular network and its regulation.
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Affiliation(s)
- Guanghong Wei
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), and Department of Physics, Fudan University, Shanghai, P. R. China
| | - Wenhui Xi
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), and Department of Physics, Fudan University, Shanghai, P. R. China
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, Maryland 21702, USA
- Sackler Inst. of Molecular Medicine Department of Human Genetics and Molecular Medicine Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, Maryland 21702, USA
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146
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Lin X, Sun X, Luo S, Liu B, Yang C. Development of DNA-based signal amplification and microfluidic technology for protein assay: A review. Trends Analyt Chem 2016. [DOI: 10.1016/j.trac.2016.02.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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147
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Reppert M, Tokmakoff A. Computational Amide I 2D IR Spectroscopy as a Probe of Protein Structure and Dynamics. Annu Rev Phys Chem 2016; 67:359-86. [DOI: 10.1146/annurev-physchem-040215-112055] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mike Reppert
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637;
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637;
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148
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Ramakrishnan S, Krainer G, Grundmeier G, Schlierf M, Keller A. Structural stability of DNA origami nanostructures in the presence of chaotropic agents. NANOSCALE 2016; 8:10398-10405. [PMID: 27142120 DOI: 10.1039/c6nr00835f] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
DNA origami represent powerful platforms for single-molecule investigations of biomolecular processes. The required structural integrity of the DNA origami may, however, pose significant limitations regarding their applicability, for instance in protein folding studies that require strongly denaturing conditions. Here, we therefore report a detailed study on the stability of 2D DNA origami triangles in the presence of the strong chaotropic denaturing agents urea and guanidinium chloride (GdmCl) and its dependence on concentration and temperature. At room temperature, the DNA origami triangles are stable up to at least 24 h in both denaturants at concentrations as high as 6 M. At elevated temperatures, however, structural stability is governed by variations in the melting temperature of the individual staple strands. Therefore, the global melting temperature of the DNA origami does not represent an accurate measure of their structural stability. Although GdmCl has a stronger effect on the global melting temperature, its attack results in less structural damage than observed for urea under equivalent conditions. This enhanced structural stability most likely originates from the ionic nature of GdmCl. By rational design of the arrangement and lengths of the individual staple strands used for the folding of a particular shape, however, the structural stability of DNA origami may be enhanced even further to meet individual experimental requirements. Overall, their high stability renders DNA origami promising platforms for biomolecular studies in the presence of chaotropic agents, including single-molecule protein folding or structural switching.
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Affiliation(s)
- Saminathan Ramakrishnan
- Technical and Macromolecular Chemistry, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany.
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149
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Schuler B, Soranno A, Hofmann H, Nettels D. Single-Molecule FRET Spectroscopy and the Polymer Physics of Unfolded and Intrinsically Disordered Proteins. Annu Rev Biophys 2016; 45:207-31. [PMID: 27145874 DOI: 10.1146/annurev-biophys-062215-010915] [Citation(s) in RCA: 221] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The properties of unfolded proteins have long been of interest because of their importance to the protein folding process. Recently, the surprising prevalence of unstructured regions or entirely disordered proteins under physiological conditions has led to the realization that such intrinsically disordered proteins can be functional even in the absence of a folded structure. However, owing to their broad conformational distributions, many of the properties of unstructured proteins are difficult to describe with the established concepts of structural biology. We have thus seen a reemergence of polymer physics as a versatile framework for understanding their structure and dynamics. An important driving force for these developments has been single-molecule spectroscopy, as it allows structural heterogeneity, intramolecular distance distributions, and dynamics to be quantified over a wide range of timescales and solution conditions. Polymer concepts provide an important basis for relating the physical properties of unstructured proteins to folding and function.
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Affiliation(s)
- Benjamin Schuler
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland;
| | - Andrea Soranno
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland;
| | - Hagen Hofmann
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland;
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland;
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Best RB, Hofmann H, Nettels D, Schuler B. Quantitative interpretation of FRET experiments via molecular simulation: force field and validation. Biophys J 2016; 108:2721-31. [PMID: 26039173 DOI: 10.1016/j.bpj.2015.04.038] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 04/23/2015] [Accepted: 04/27/2015] [Indexed: 12/14/2022] Open
Abstract
Molecular simulation is a valuable and complementary tool that may assist with the interpretation of single-molecule Förster resonance energy transfer (FRET) experiments, if the energy function is of sufficiently high quality. Here we present force-field parameters for one of the most common pairs of chromophores used in experiments, AlexaFluor 488 and 594. From microsecond molecular-dynamics simulations, we are able to recover both experimentally determined equilibrium constants and association/dissociation rates of the chromophores with free tryptophan, as well as the decay of fluorescence anisotropy of a labeled protein. We find that it is particularly important to obtain a correct balance of solute-water interactions in the simulations in order to faithfully capture the experimental anisotropy decays, which provide a sensitive benchmark for fluorophore mobility. Lastly, by a combination of experiment and simulation, we address a potential complication in the interpretation of experiments on polyproline, used as a molecular ruler for FRET experiments, namely the potential association of one of the chromophores with the polyproline helix. Under conditions where simulations accurately capture the fluorescence anisotropy decay, we find at most a modest, transient population of conformations in which the chromophores associate with the polyproline. Explicit calculation of FRET transfer efficiencies for short polyprolines yields results in good agreement with experiment. These results illustrate the potential power of a combination of molecular simulation and experiment in quantifying biomolecular dynamics.
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Affiliation(s)
- Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
| | - Hagen Hofmann
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Daniel Nettels
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Benjamin Schuler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.
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