1
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Sano Y, Itoh Y, Kamonprasertsuk S, Suzuki L, Fukasawa A, Oikawa H, Takahashi S. Simple and Efficient Detection Scheme of Two-Color Fluorescence Correlation Spectroscopy for Protein Dynamics Investigation from Nanoseconds to Milliseconds. ACS PHYSICAL CHEMISTRY AU 2024; 4:85-93. [PMID: 38283787 PMCID: PMC10811772 DOI: 10.1021/acsphyschemau.3c00040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/29/2023] [Accepted: 10/30/2023] [Indexed: 01/30/2024]
Abstract
Nanosecond resolved fluorescence correlation spectroscopy (ns-FCS) based on two-color fluorescence detection is a powerful strategy for investigating the fast dynamics of biological macromolecules labeled with donor and acceptor fluorophores. The standard methods of ns-FCS use two single-photon avalanche diodes (SPADs) for the detection of single-color signals (four SPADs for two-color signals) to eliminate the afterpulse artifacts of SPAD at the expense of the efficiency of utilizing photon data in the calculation of correlograms. Herein, we demonstrated that hybrid photodetectors (HPDs) enable the recording of fluorescence photons in ns-FCS based on the minimal system using two HPDs for the detection of two-color signals. However, HPD exhibited afterpulses at a yield with respect to the rate of photodetection (<10-4) much lower than that of SPADs (∼10-2), which could still hamper correlation measurements. We demonstrated that the simple subtraction procedure could eliminate afterpulse artifacts. While the quantum efficiency of photodetection for HPDs is lower than that for high-performance SPADs, the developed system can be practically used for two-color ns-FCS in a time domain longer than a few nanoseconds. The fast chain dynamics of the B domain of protein A in the unfolded state was observed using the new method.
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Affiliation(s)
- Yutaka Sano
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Department of Chemistry, Graduate School of Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Department of Chemistry, Graduate School of Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Supawich Kamonprasertsuk
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Department of Chemistry, Graduate School of Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Leo Suzuki
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Atsuhito Fukasawa
- Electron Tube Division, Hamamatsu Photonics K. K., Iwata, Shizuoka 438-0193, Japan
| | - Hiroyuki Oikawa
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Department of Chemistry, Graduate School of Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan
- MOLCURE, Kawasaki, Kanagawa 212-0032, Japan
| | - Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan
- Department of Chemistry, Graduate School of Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8577, Japan
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2
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Santhouse JR, Leung JMG, Chong LT, Horne WS. Effects of altered backbone composition on the folding kinetics and mechanism of an ultrafast-folding protein. Chem Sci 2024; 15:675-682. [PMID: 38179541 PMCID: PMC10763558 DOI: 10.1039/d3sc03976e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 12/02/2023] [Indexed: 01/06/2024] Open
Abstract
Sequence-encoded protein folding is a ubiquitous biological process that has been successfully engineered in a range of oligomeric molecules with artificial backbone chemical connectivity. A remarkable aspect of protein folding is the contrast between the rapid rates at which most sequences in nature fold and the vast number of conformational states possible in an unfolded chain with hundreds of rotatable bonds. Research efforts spanning several decades have sought to elucidate the fundamental chemical principles that dictate the speed and mechanism of natural protein folding. In contrast, little is known about how protein mimetic entities transition between an unfolded and folded state. Here, we report effects of altered backbone connectivity on the folding kinetics and mechanism of the B domain of Staphylococcal protein A (BdpA), an ultrafast-folding sequence. A combination of experimental biophysical analysis and atomistic molecular dynamics simulations performed on the prototype protein and several heterogeneous-backbone variants reveal the interplay among backbone flexibility, folding rates, and structural details of the transition state ensemble. Collectively, these findings suggest a significant degree of plasticity in the mechanisms that can give rise to ultrafast folding in the BdpA sequence and provide atomic level insights into how protein mimetic chains adopt an ordered folded state.
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Affiliation(s)
| | - Jeremy M G Leung
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Lillian T Chong
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - W Seth Horne
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
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3
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Yanaka S, Yagi-Utsumi M, Kato K, Kuwajima K. The B domain of protein A retains residual structures in 6 M guanidinium chloride as revealed by hydrogen/deuterium-exchange NMR spectroscopy. Protein Sci 2023; 32:e4569. [PMID: 36659853 PMCID: PMC9926473 DOI: 10.1002/pro.4569] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 01/10/2023] [Accepted: 01/13/2023] [Indexed: 01/21/2023]
Abstract
The characterization of residual structures persistent in unfolded proteins is an important issue in studies of protein folding, because the residual structures present, if any, may form a folding initiation site and guide the subsequent folding reactions. Here, we studied the residual structures of the isolated B domain (BDPA) of staphylococcal protein A in 6 M guanidinium chloride. BDPA is a small three-helix-bundle protein, and until recently its folding/unfolding reaction has been treated as a simple two-state process between the native and the fully unfolded states. We employed a dimethylsulfoxide (DMSO)-quenched hydrogen/deuterium (H/D)-exchange 2D NMR techniques with the use of spin desalting columns, which allowed us to investigate the H/D-exchange behavior of individually identified peptide amide (NH) protons. We obtained H/D-exchange protection factors of the 21 NH protons that form an α-helical hydrogen bond in the native structure, and the majority of these NH protons were significantly protected with a protection factor of 2.0-5.2 in 6 M guanidinium chloride, strongly suggesting that these weakly protected NH protons form much stronger hydrogen bonds under native folding conditions. The results can be used to deduce the structure of an early folding intermediate, when such an intermediate is shown by other methods. Among three native helical regions, the third helix in the C-terminal side was highly protected and stabilized by side-chain salt bridges, probably acting as the folding initiation site of BDPA. The present results are discussed in relation to previous experimental and computational findings on the folding mechanisms of BDPA.
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Affiliation(s)
- Saeko Yanaka
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, Myodaiji, Okazaki, Aichi, Japan.,Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (the Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Aichi, Japan
| | - Maho Yagi-Utsumi
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, Myodaiji, Okazaki, Aichi, Japan.,Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (the Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Aichi, Japan
| | - Koichi Kato
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, Myodaiji, Okazaki, Aichi, Japan.,Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (the Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Aichi, Japan
| | - Kunihiro Kuwajima
- Department of Physics, School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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4
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Mitra S, Oikawa H, Rajendran D, Kowada T, Mizukami S, Naganathan AN, Takahashi S. Flexible Target Recognition of the Intrinsically Disordered DNA-Binding Domain of CytR Monitored by Single-Molecule Fluorescence Spectroscopy. J Phys Chem B 2022; 126:6136-6147. [PMID: 35969476 PMCID: PMC9422980 DOI: 10.1021/acs.jpcb.2c02791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/03/2022] [Indexed: 11/29/2022]
Abstract
The intrinsically disordered DNA-binding domain of cytidine repressor (CytR-DBD) folds in the presence of target DNA and regulates the expression of multiple genes in E. coli. To explore the conformational rearrangements in the unbound state and the target recognition mechanisms of CytR-DBD, we carried out single-molecule Förster resonance energy transfer (smFRET) measurements. The smFRET data of CytR-DBD in the absence of DNA show one major and one minor population assignable to an expanded unfolded state and a compact folded state, respectively. The population of the folded state increases and decreases upon titration with salt and denaturant, respectively, in an apparent two-state manner. The peak FRET efficiencies of both the unfolded and folded states change continuously with denaturant concentration, demonstrating the intrinsic flexibility of the DNA-binding domain and the deviation from a strict two-state transition. Remarkably, the CytR-DBD exhibits a compact structure when bound to both the specific and nonspecific DNA; however, the peak FRET efficiencies of the two structures are slightly but consistently different. The observed conformational heterogeneity highlights the potential structural changes required for CytR to bind variably spaced operator sequences.
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Affiliation(s)
- Shrutarshi Mitra
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Hiroyuki Oikawa
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Divya Rajendran
- Department
of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Toshiyuki Kowada
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Shin Mizukami
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Athi N. Naganathan
- Department
of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Satoshi Takahashi
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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5
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Abstract
Proteins have dynamic structures that undergo chain motions on time scales spanning from picoseconds to seconds. Resolving the resultant conformational heterogeneity is essential for gaining accurate insight into fundamental mechanistic aspects of the protein folding reaction. The use of high-resolution structural probes, sensitive to population distributions, has begun to enable the resolution of site-specific conformational heterogeneity at different stages of the folding reaction. Different states populated during protein folding, including the unfolded state, collapsed intermediate states, and even the native state, are found to possess significant conformational heterogeneity. Heterogeneity in protein folding and unfolding reactions originates from the reduced cooperativity of various kinds of physicochemical interactions between various structural elements of a protein, and between a protein and solvent. Heterogeneity may arise because of functional or evolutionary constraints. Conformational substates within the unfolded state and the collapsed intermediates that exchange at rates slower than the subsequent folding steps give rise to heterogeneity on the protein folding pathways. Multiple folding pathways are likely to represent distinct sequences of structure formation. Insight into the nature of the energy barriers separating different conformational states populated during (un)folding can also be obtained by resolving heterogeneity.
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Affiliation(s)
- Sandhya Bhatia
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.,Indian Institute of Science Education and Research, Pune 411008, India
| | - Jayant B Udgaonkar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.,Indian Institute of Science Education and Research, Pune 411008, India
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6
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Kamagata K, Kanbayashi S, Honda M, Itoh Y, Takahashi H, Kameda T, Nagatsugi F, Takahashi S. Liquid-like droplet formation by tumor suppressor p53 induced by multivalent electrostatic interactions between two disordered domains. Sci Rep 2020; 10:580. [PMID: 31953488 PMCID: PMC6969132 DOI: 10.1038/s41598-020-57521-w] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 12/13/2019] [Indexed: 12/25/2022] Open
Abstract
Early in vivo studies demonstrated the involvement of a tumor-suppressing transcription factor, p53, into cellular droplets such as Cajal and promyelocytic leukemia protein bodies, suggesting that the liquid-liquid phase separation (LLPS) might be involved in the cellular functions of p53. To examine this possibility, we conducted extensive investigations on the droplet formation of p53 in vitro. First, p53 itself was found to form liquid-like droplets at neutral and slightly acidic pH and at low salt concentrations. Truncated p53 mutants modulated droplet formation, suggesting the importance of multivalent electrostatic interactions among the N-terminal and C-terminal domains. Second, FRET efficiency measurements for the dimer mutants of p53 revealed that distances between the core domains and between the C-terminal domains were modulated in an opposite manner within the droplets. Third, the molecular crowding agents were found to promote droplet formation, whereas ssDNA, dsDNA, and ATP, to suppress it. Finally, the p53 mutant mimicking posttranslational phosphorylation did not form the droplets. We conclude that p53 itself has a potential to form droplets that can be controlled by cellular molecules and by posttranslational modifications, suggesting that LLPS might be involved in p53 function.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan. .,Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.
| | - Saori Kanbayashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan
| | - Masaya Honda
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.,Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan
| | - Hiroto Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan
| | - Tomoshi Kameda
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Koto, Tokyo, 135-0064, Japan
| | - Fumi Nagatsugi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.,Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.,Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
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7
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High-throughput smFRET analysis of freely diffusing nucleic acid molecules and associated proteins. Methods 2019; 169:21-45. [PMID: 31356875 DOI: 10.1016/j.ymeth.2019.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 06/24/2019] [Accepted: 07/22/2019] [Indexed: 11/21/2022] Open
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a powerful technique for nanometer-scale studies of single molecules. Solution-based smFRET, in particular, can be used to study equilibrium intra- and intermolecular conformations, binding/unbinding events and conformational changes under biologically relevant conditions without ensemble averaging. However, single-spot smFRET measurements in solution are slow. Here, we detail a high-throughput smFRET approach that extends the traditional single-spot confocal geometry to a multispot one. The excitation spots are optically conjugated to two custom silicon single photon avalanche diode (SPAD) arrays. Two-color excitation is implemented using a periodic acceptor excitation (PAX), allowing distinguishing between singly- and doubly-labeled molecules. We demonstrate the ability of this setup to rapidly and accurately determine FRET efficiencies and population stoichiometries by pooling the data collected independently from the multiple spots. We also show how the high throughput of this approach can be used o increase the temporal resolution of single-molecule FRET population characterization from minutes to seconds. Combined with microfluidics, this high-throughput approach will enable simple real-time kinetic studies as well as powerful molecular screening applications.
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8
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Otosu T, Yamaguchi S. Two-Dimensional Fluorescence Lifetime Correlation Spectroscopy: Concepts and Applications. Molecules 2018; 23:E2972. [PMID: 30441830 PMCID: PMC6278346 DOI: 10.3390/molecules23112972] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 11/07/2018] [Accepted: 11/13/2018] [Indexed: 01/03/2023] Open
Abstract
We review the basic concepts and recent applications of two-dimensional fluorescence lifetime correlation spectroscopy (2D FLCS), which is the extension of fluorescence correlation spectroscopy (FCS) to analyze the correlation of fluorescence lifetime in addition to fluorescence intensity. Fluorescence lifetime is sensitive to the microenvironment and can be a "molecular ruler" when combined with FRET. Utilization of fluorescence lifetime in 2D FLCS thus enables us to quantify the inhomogeneity of the system and the interconversion dynamics among different species with a higher time resolution than other single-molecule techniques. Recent applications of 2D FLCS to various biological systems demonstrate that 2D FLCS is a unique and promising tool to quantitatively analyze the microsecond conformational dynamics of macromolecules at the single-molecule level.
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Affiliation(s)
- Takuhiro Otosu
- Department of Applied Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan.
| | - Shoichi Yamaguchi
- Department of Applied Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan.
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9
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Takahashi S, Yoshida A, Oikawa H. Hypothesis: structural heterogeneity of the unfolded proteins originating from the coupling of the local clusters and the long-range distance distribution. Biophys Rev 2018; 10:363-373. [PMID: 29446056 DOI: 10.1007/s12551-018-0405-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 02/05/2018] [Indexed: 01/22/2023] Open
Abstract
We propose a hypothesis that explains two apparently contradicting observations for the heterogeneity of the unfolded proteins. First, the line confocal method of the single-molecule Förster resonance energy transfer (sm-FRET) spectroscopy revealed that the unfolded proteins possess broad peaks in the FRET efficiency plot, implying the significant heterogeneity that lasts longer than milliseconds. Second, the fluorescence correlation method demonstrated that the unfolded proteins fluctuate in the time scale shorter than 100 ns. To formulate the hypothesis, we first summarize the recent consensus for the structure and dynamics of the unfolded proteins. We next discuss the conventional method of the sm-FRET spectroscopy and its limitations for the analysis of the unfolded proteins, followed by the advantages of the line confocal method that revealed the heterogeneity. Finally, we propose that the structural heterogeneity formed by the local clustering of hydrophobic residues modulates the distribution of the long-range distance between the labeled chromophores, resulting in the broadening of the peak in the FRET efficiency plot. A clustering of hydrophobic residues around the chromophore might further contribute to the broadening. The proposed clusters are important for the understanding of protein folding mechanism.
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Affiliation(s)
- Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan. .,Department of Chemistry, Graduate school of Science, Tohoku University, Aramaki 6-3, Aoba-ku, Sendai, 980-8578, Japan.
| | - Aya Yoshida
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.,Department of Chemistry, Graduate school of Science, Tohoku University, Aramaki 6-3, Aoba-ku, Sendai, 980-8578, Japan
| | - Hiroyuki Oikawa
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.,Department of Chemistry, Graduate school of Science, Tohoku University, Aramaki 6-3, Aoba-ku, Sendai, 980-8578, Japan
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10
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Oikawa H, Takahashi T, Kamonprasertsuk S, Takahashi S. Microsecond resolved single-molecule FRET time series measurements based on the line confocal optical system combined with hybrid photodetectors. Phys Chem Chem Phys 2018; 20:3277-3285. [PMID: 29138775 DOI: 10.1039/c7cp06268k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Single-molecule (sm) fluorescence time series measurements based on the line confocal optical system are a powerful strategy for the investigation of the structure, dynamics, and heterogeneity of biological macromolecules. This method enables the detection of more than several thousands of fluorescence photons per millisecond from single fluorophores, implying that the potential time resolution for measurements of the fluorescence resonance energy transfer (FRET) efficiency is 10 μs. However, the necessity of using imaging photodetectors in the method limits the time resolution in the FRET efficiency measurements to approximately 100 μs. In this investigation, a new photodetector called a hybrid photodetector (HPD) was incorporated into the line confocal system to improve the time resolution without sacrificing the length of the time series detection. Among several settings examined, the system based on a slit width of 10 μm and a high-speed counting device made the best of the features of the line confocal optical system and the HPD. This method achieved a time resolution of 10 μs and an observation time of approximately 5 ms in the sm-FRET time series measurements. The developed device was used for the native state of the B domain of protein A.
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Affiliation(s)
- Hiroyuki Oikawa
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, Miyagi 980-8577, Japan.
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11
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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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12
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Otosu T, Ishii K, Oikawa H, Arai M, Takahashi S, Tahara T. Highly Heterogeneous Nature of the Native and Unfolded States of the B Domain of Protein A Revealed by Two-Dimensional Fluorescence Lifetime Correlation Spectroscopy. J Phys Chem B 2017; 121:5463-5473. [DOI: 10.1021/acs.jpcb.7b00546] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Kunihiko Ishii
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
| | - Hiroyuki Oikawa
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1
Katahira, Aoba, Sendai, Miyagi 980-8577, Japan
| | - Munehito Arai
- Department
of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
| | - Satoshi Takahashi
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1
Katahira, Aoba, Sendai, Miyagi 980-8577, Japan
| | - Tahei Tahara
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
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13
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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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14
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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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15
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Stockmar F, Kobitski AY, Nienhaus GU. Fast Folding Dynamics of an Intermediate State in RNase H Measured by Single-Molecule FRET. J Phys Chem B 2016; 120:641-9. [PMID: 26747376 DOI: 10.1021/acs.jpcb.5b09336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied the folding kinetics of the core intermediate (I) state of RNase H by using a combination of single-molecule FRET (smFRET) and hidden Markov model analysis. To measure fast dynamics in thermal equilibrium as a function of the concentration of the denaturant GdmCl, a special FRET labeled variant, RNase H 60-113, which is sensitive to folding of the protein core, was immobilized on PEGylated surfaces. Conformational transitions between the unfolded (U) state and the I state could be described by a two-state model within our experimental time resolution, with millisecond mean residence times. The I state population was always a minority species in the entire accessible range of denaturant concentrations. By introducing the measured free energy differences between the U and I states as constraints in global fits of the GdmCl dependence of FRET histograms of a differently labeled RNase H variant (RNase H 3-135), we were able to reveal the free energy differences and, thus, population ratios of all three macroscopic state ensembles, U, I and F (folded state) as a function of denaturant concentration.
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Affiliation(s)
- Florian Stockmar
- Institute of Applied Physics, Karlsruhe Institute of Technology (KIT) , Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany
| | - Andrei Yu Kobitski
- Institute of Applied Physics, Karlsruhe Institute of Technology (KIT) , Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany
| | - Gerd Ulrich Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology (KIT) , Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.,Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.,Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.,Department of Physics, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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16
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17
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Where the complex things are: single molecule and ensemble spectroscopic investigations of protein folding dynamics. Curr Opin Struct Biol 2015; 36:1-9. [PMID: 26687767 DOI: 10.1016/j.sbi.2015.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 11/10/2015] [Indexed: 01/11/2023]
Abstract
Progress in our understanding of the simple folding dynamics of small proteins and the complex dynamics of large proteins is reviewed. Recent characterizations of the folding transition path of small proteins revealed a simple dynamics explainable by the native centric model. In contrast, the accumulated data showed the substates containing residual structures in the unfolded state and partially populated intermediates, causing complexity in the early folding dynamics of small proteins. The size of the unfolded proteins in the absence of denaturants is likely expanded but still controversial. The steady progress in the observation of folding of large proteins has clarified the rapid formation of long-range contacts that seem inconsistent with the native centric model, suggesting that the folding strategy of large proteins is distinct from that of small proteins.
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