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Baek SH, Yun J, Lee SH, Lee HW, Kwon Y, Park KR, Song Y, Kim BS, Kwak R, Hwang H, Jeong DW. Real-time analysis and prediction method of ion concentration using the effect of O-H stretching bands in aqueous solutions based on ATR-FTIR spectroscopy. RSC Adv 2024; 14:20073-20080. [PMID: 38915330 PMCID: PMC11194664 DOI: 10.1039/d4ra01473a] [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: 02/26/2024] [Accepted: 06/14/2024] [Indexed: 06/26/2024] Open
Abstract
Analyzing the concentration of ions in aqueous solutions in real-time plays an important role in the fields of chemistry and biology. Traditional methods for measuring ion concentrations, such as concentration analysis by measuring electrical conductivity, inductively coupled plasma mass spectrometry, and ion chromatography, have been used in many research fields. However, these methods are limited in determining ion concentrations instantaneously. Fourier-transform infrared-attenuated total reflectance (ATR-FTIR) spectroscopy provides a new approach for determining ion concentrations in aqueous solutions. This allows for fast analysis without pretreatment and is scalable for real-time measurements. In this study, we present a method for measuring ion concentrations by examining ion-water interactions in the O-H stretching band of aqueous solutions using ATR-FTIR spectroscopy. Five aqueous solutions, namely LiCl + HCl, LiOH + HCl, LiOH, Li3PO4, and NaCl were used in the experiments and prepared at concentrations between 0.5-2 M. The ion concentrations in the prepared aqueous solutions were measured using ATR-FTIR spectroscopy. We observed that the difference in absorbance increased and decreased linearly with changes in concentration. The concentration of ions in the aqueous solution could be measured by validating the designed linear regression analysis function model. In this study, we proposed five linear regression analysis function models, all of which showed high coefficients of determination above 0.9, with the highest coefficient of determination reaching 0.9969. These results show that ATR-FTIR spectroscopy has the potential to be applied as a rapid and simple concentration analysis system.
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Affiliation(s)
- So Hyun Baek
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
- Department of Material Science Engineering, Inha University Incheon 22212 Republic of Korea
| | - Jeungjai Yun
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
- Department of Mechanical Convergence Engineering, Hanyang University Seoul 04763 Republic of Korea
| | - Seung-Hwan Lee
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Hyun-Woo Lee
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Yongbum Kwon
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Kee-Ryung Park
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Yoseb Song
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Bum Sung Kim
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
| | - Rhokyun Kwak
- Department of Mechanical Convergence Engineering, Hanyang University Seoul 04763 Republic of Korea
| | - Haejin Hwang
- Department of Material Science Engineering, Inha University Incheon 22212 Republic of Korea
| | - Da-Woon Jeong
- Department of Korea National Institute of Rare Metals, Korea Institute of Industrial Technology Incheon 21655 Republic of Korea +82-32-226-1374 +82-32-226-1362
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2
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Zhao X, Ding W, Wang H, Wang Y, Liu Y, Li Y, Liu C. Structural Insights and Influence of Terahertz Waves in Midinfrared Region on Kv1.2 Channel Selectivity Filter. ACS OMEGA 2024; 9:9702-9713. [PMID: 38434859 PMCID: PMC10905694 DOI: 10.1021/acsomega.3c09801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 03/05/2024]
Abstract
Potassium ion channels are the structural basis for excitation transmission, heartbeat, and other biological processes. The selectivity filter is a critical structural component of potassium ion channels, whose structure is crucial to realizing their function. As biomolecules vibrate and rotate at frequencies in the terahertz band, potassium ion channels are sensitive to terahertz waves. Therefore, it is worthwhile to investigate how the terahertz wave influences the selectivity filter of the potassium channels. In this study, we investigate the structure of the selectivity filter of Kv1.2 potassium ion channels using molecular dynamics simulations. The effect of an electric field on the channel has been examined at four different resonant frequencies of the carbonyl group in SF: 36.75 37.06, 37.68, and 38.2 THz. As indicated by the results, 376GLY appears to be the critical residue in the selectivity filter of the Kv1.2 channel. Its dihedral angle torsion is detrimental to the channel structural stability and the transmembrane movement of potassium ions. 36.75 THz is the resonance frequency of the carbonyl group of 376GLY. Among all four frequencies explored, the applied terahertz electric field of this frequency has the most significant impact on the channel structure, negatively impacting the channel stability and reducing the ion permeability by 20.2% compared to the absence of fields. In this study, we simulate that terahertz waves in the mid-infrared frequency region can significantly alter the structure and function of potassium ion channels and that the effects of terahertz waves differ greatly based on frequency.
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Affiliation(s)
- Xiaofei Zhao
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Wen Ding
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Hongguang Wang
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Yize Wang
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Yanjiang Liu
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Yongdong Li
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Chunliang Liu
- Key Laboratory
for Physical
Electronics and Devices of the Ministry of Education, School of Electronic
and Information Engineering, Xi’an
Jiaotong University, Xi’an, Shaanxi 710049, China
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3
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Hashimoto M, Miyagawa K, Singh M, Katayama K, Shoji M, Furutani Y, Shigeta Y, Kandori H. Specific zinc binding to heliorhodopsin. Phys Chem Chem Phys 2023; 25:3535-3543. [PMID: 36637167 DOI: 10.1039/d2cp04718g] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Heliorhodopsins (HeRs), a recently discovered family of rhodopsins, have an inverted membrane topology compared to animal and microbial rhodopsins. The slow photocycle of HeRs suggests a light-sensor function, although the actual function remains unknown. Although HeRs exhibit no specific binding of monovalent cations or anions, recent ATR-FTIR spectroscopy studies have demonstrated the binding of Zn2+ to HeR from Thermoplasmatales archaeon (TaHeR) and 48C12. Even though ion-specific FTIR spectra were observed for many divalent cations, only helical structural perturbations were observed for Zn2+-binding, suggesting a possible modification of the HeR function by Zn2+. The present study shows that Zn2+-binding lowers the thermal stability of TaHeR, and slows back proton transfer to the retinal Schiff base (M decay) during its photocycle. Zn2+-binding was similarly observed for a TaHeR opsin that lacks the retinal chromophore. We then studied the Zn2+-binding site by means of the ATR-FTIR spectroscopy of site-directed mutants. Among five and four mutants of His and Asp/Glu, respectively, only E150Q exhibited a completely different spectral feature of the α-helix (amide-I) in ATR-FTIR spectroscopy, suggesting that E150 is responsible for Zn2+-binding. Molecular dynamics (MD) simulations built a coordination structure of Zn2+-bound TaHeR, where E150 and protein bound water molecules participate in direct coordination. It was concluded that the specific binding site of Zn2+ is located at the cytoplasmic side of TaHeR, and that Zn2+-binding affects the structure and structural dynamics, possibly modifying the unknown function of TaHeR.
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Affiliation(s)
- Masanori Hashimoto
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
| | - Koichi Miyagawa
- Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan.
| | - Manish Singh
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
| | - Kota Katayama
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan. .,OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.,JST-PRESTO, Kawaguchi, Saitama 332-0012, Japan
| | - Mitsuo Shoji
- Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan. .,JST-PRESTO, Kawaguchi, Saitama 332-0012, Japan
| | - Yuji Furutani
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan. .,OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan.
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan. .,OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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4
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Hirano T, Yazawa N, Wang L, Morita A. Development of Efficient Computational Analysis of Difference Infrared and Raman Spectroscopies. J Chem Phys 2022; 157:124105. [DOI: 10.1063/5.0108934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Computational analysis of difference spectra between two analogous systems is a challenging issue, as reliable estimation of a tiny difference spectrum requires an extraordinary precision of the two original spectra. We have developed an alternative new method to calculate the difference spectra in background-free conditions, which greatly improved the efficiency of computation. In this paper we report further improvement by using efficient parallel implementation and the time correlation formula based on time derivative quantities. As a consequence, the present work achieved further remarkable acceleration in the calculations of difference infrared and Raman spectra in the order of magnitude, and thereby allowed us with analyzing these difference spectra at a practical cost of computation.
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Affiliation(s)
| | | | - Lin Wang
- Tohoku University Graduate School of Science Faculty of Science, Japan
| | - Akihiro Morita
- Department of Chemistry, Tohoku University - Aobayama Campus, Japan
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5
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Kandori H. Structure/Function Study of Photoreceptive Proteins by FTIR Spectroscopy. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20200109] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Hideki Kandori
- Department of Life Science and Applied Chemistry & OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
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6
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Abstract
Infrared difference spectroscopy probes vibrational changes of proteins upon their perturbation. Compared with other spectroscopic methods, it stands out by its sensitivity to the protonation state, H-bonding, and the conformation of different groups in proteins, including the peptide backbone, amino acid side chains, internal water molecules, or cofactors. In particular, the detection of protonation and H-bonding changes in a time-resolved manner, not easily obtained by other techniques, is one of the most successful applications of IR difference spectroscopy. The present review deals with the use of perturbations designed to specifically change the protein between two (or more) functionally relevant states, a strategy often referred to as reaction-induced IR difference spectroscopy. In the first half of this contribution, I review the technique of reaction-induced IR difference spectroscopy of proteins, with special emphasis given to the preparation of suitable samples and their characterization, strategies for the perturbation of proteins, and methodologies for time-resolved measurements (from nanoseconds to minutes). The second half of this contribution focuses on the spectral interpretation. It starts by reviewing how changes in H-bonding, medium polarity, and vibrational coupling affect vibrational frequencies, intensities, and bandwidths. It is followed by band assignments, a crucial aspect mostly performed with the help of isotopic labeling and site-directed mutagenesis, and complemented by integration and interpretation of the results in the context of the studied protein, an aspect increasingly supported by spectral calculations. Selected examples from the literature, predominately but not exclusively from retinal proteins, are used to illustrate the topics covered in this review.
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7
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Sumikama T, Oiki S. Queueing arrival and release mechanism for K + permeation through a potassium channel. J Physiol Sci 2019; 69:919-930. [PMID: 31456113 PMCID: PMC10717923 DOI: 10.1007/s12576-019-00706-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 08/18/2019] [Indexed: 01/26/2023]
Abstract
The mechanism underlying ion permeation through potassium channels still remains controversial. K+ ions permeate across a narrow selectivity filter (SF) in a single file. Conventional scenarios assume that K+ ions are tightly bound in the SF, and, thus, they are displaced from their energy well by ion-ion repulsion with an incoming ion. This tight coupling between entering and exiting ions has been called the "knock-on" mechanism. However, this paradigm is contradicted by experimental data measuring the water-ion flux coupling ratio, demonstrating fewer ion occupancies. Here, the results of molecular dynamics simulations of permeation through the KcsA potassium channel revealed an alternative mechanism. In the aligned ions in the SF (an ion queue), the outermost K+ was readily and spontaneously released toward the extracellular space, and the affinity of the relevant ion was ~ 50 mM. Based on this low-affinity regime, a simple queueing mechanism described by loose coupling of entering and exiting ions is proposed.
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Affiliation(s)
- Takashi Sumikama
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.
- Biomedical Imaging Research Center, University of Fukui, Fukui, 910-1193, Japan.
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8
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Ishiuchi SI, Sasaki Y, Lisy JM, Fujii M. Ion-peptide interactions between alkali metal ions and a termini-protected dipeptide: modeling a portion of the selectivity filter in K + channels. Phys Chem Chem Phys 2019; 21:561-571. [PMID: 30351321 DOI: 10.1039/c8cp05839c] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Potassium channels have the unique ability to allow the selective passage of potassium ions at near diffusion-free rates while inhibiting the passage of more abundant sodium ions. Local interactions between chemical functional groups and the ions are responsible for both selectivity and transport. As an initial step in characterizing these interactions, the structures of Na+ and K+ complexed to the Ac-Tyr-NHMe peptide have been determined from infrared laser spectroscopy and supporting ab initio calculations. Ac-Tyr-NHMe, a termini-protected peptide sequence, replicates the GYG portion of one of the four peptide chains comprising the selectivity filter of a K+ channel. This peptide contains two carbonyl groups, among the eight C[double bond, length as m-dash]O groups forming the S1 binding site of the selectivity filter. Three conformations have been identified for both ions by laser IR-IR double resonance methods. Two conformations have the ion bound to the two C[double bond, length as m-dash]O groups. The third conformation has, in addition, a cation-π interaction with the aromatic ring of tyrosine, i.e. tridentate binding. The relative contributions of the three conformers are approximately the same for K+Ac-Tyr-NHMe, while the tridentate conformer is preferred for Na+Ac-Tyr-NHMe. These differences will be discussed in the context of ion mobility and selectivity.
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Affiliation(s)
- Shun-Ichi Ishiuchi
- Laboratory for Chemistry and Life Science, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
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9
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Kimura T, Lorenz-Fonfria VA, Douki S, Motoki H, Ishitani R, Nureki O, Higashi M, Furutani Y. Vibrational and Molecular Properties of Mg2+ Binding and Ion Selectivity in the Magnesium Channel MgtE. J Phys Chem B 2018; 122:9681-9696. [DOI: 10.1021/acs.jpcb.8b07967] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Tetsunari Kimura
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Victor A. Lorenz-Fonfria
- Institute of Molecular Science (ICMol), Universitat de València, Catedràtic José Beltrán Martínez 2, 46980 Paterna, Spain
- Department of Biochemistry and Molecular Biology, Universitat de València, Carrer Doctor Moliner 50, 46100 Burjassot, Spain
| | - Shintaro Douki
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideyoshi Motoki
- Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213, Japan
| | - Ryuichiro Ishitani
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Osamu Nureki
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masahiro Higashi
- Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213, Japan
| | - Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
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10
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Iwaki M, Takeshita K, Kondo HX, Kinoshita K, Okamura Y, Takano Y, Nakagawa A, Kandori H. Zn2+-Binding to the Voltage-Gated Proton Channel Hv1/VSOP. J Phys Chem B 2018; 122:9076-9080. [DOI: 10.1021/acs.jpcb.8b04890] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Hiroko X. Kondo
- Department of Biomedical Information Sciences, Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozuka-Higashi, Asa-Minami-Ku, Hiroshima 731-3194, Japan
- Laboratory for Computational Molecular Design, RIKEN Center for Biosystems Dynamics Research, 6-2-3, Furuedai, Suita, 565-0874, Japan
| | - Kengo Kinoshita
- Department of Applied Information Sciences, Graduate School of Information Sciences, Tohoku University, 6-3-09 Aramaki-Aza-Aoba, Aoba-ku, Sendai, 980-8579, Japan
- Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seityo-machi, Aoba-ku, Sendai, 980-8573, Japan
- Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryocho, Aoba-ku, Sendai, 980-8575, Japan
| | | | - Yu Takano
- Department of Biomedical Information Sciences, Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozuka-Higashi, Asa-Minami-Ku, Hiroshima 731-3194, Japan
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11
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Ito S, Kandori H, Lorenz-Fonfria VA. Potential Second-Harmonic Ghost Bands in Fourier Transform Infrared (FT-IR) Difference Spectroscopy of Proteins. APPLIED SPECTROSCOPY 2018; 72:956-963. [PMID: 29350538 DOI: 10.1177/0003702818757521] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fourier transform infrared (FT-IR) difference absorption spectroscopy is a common method for studying the structural and dynamical aspects behind protein function. In particular, the 2800-1800 cm-1 spectral range has been used to obtain information about internal (deuterated) water molecules, as well as site-specific details about cysteine residues and chemically modified and artificial amino acids. Here, we report on the presence of ghost bands in cryogenic light-induced FT-IR difference spectra of the protein bacteriorhodopsin. The presence of these ghost bands can be particularly problematic in the 2800-1900 cm-1 region, showing intensities similar to O-D vibrations from water molecules. We demonstrate that they arise from second harmonics from genuine chromophore bands located in the 1400-850 cm-1 region, generated by double-modulation artifacts caused from reflections of the IR beam at the sample and at the cryostat windows back to the interferometer (inter-reflections). The second-harmonic ghost bands can be physically removed by placing an optical filter of suitable cutoff in the beam path, but at the cost of losing part of the multiplexing advantage of FT-IR spectroscopy. We explored alternatives to the use of optical filters. Tilting the cryostat windows was effective in reducing the intensity of the second harmonic artifacts but tilting the sample windows was not, presumably by their close proximity to the focal point of the IR beam. We also introduce a simple numerical post-processing approach that can partially, but not fully, correct for second-harmonic ghost bands in FT-IR difference spectra.
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Affiliation(s)
- Shota Ito
- 1 Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
| | - Hideki Kandori
- 1 Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
- 2 OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Japan
| | - Victor A Lorenz-Fonfria
- 3 Institute of Molecular Science (ICMol), Universitat de València, Paterna, Spain
- 4 Department of Biochemistry and Molecular Biology, Universitat de València, Burjassot, Spain
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12
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Tsukamoto H, Higashi M, Motoki H, Watanabe H, Ganser C, Nakajo K, Kubo Y, Uchihashi T, Furutani Y. Structural properties determining low K + affinity of the selectivity filter in the TWIK1 K + channel. J Biol Chem 2018; 293:6969-6984. [PMID: 29545310 DOI: 10.1074/jbc.ra118.001817] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 03/14/2018] [Indexed: 11/06/2022] Open
Abstract
Canonical K+ channels are tetrameric and highly K+-selective, whereas two-pore-domain K+ (K2P) channels form dimers, but with a similar pore architecture. A two-pore-domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na+ and other monovalent ions, resulting mainly from the presence of Thr-118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange-induced difference IR spectroscopy, we analyzed WT TWIK1 and T118I (highly K+-selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K+ ions, WT and both variants exhibit an amide-I band at 1680 cm-1 This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K+, a feature very similar to that of the canonical K+ channel KcsA. Computational analysis indicated that the relatively high frequency for the amide-I band is well explained by impairment of hydrogen bond formation with water molecules. Moreover, concentration-dependent spectral changes indicated that the K+ affinity of the WT selectivity filter was much lower than those of the variants. Furthermore, only the variants displayed a higher frequency shift of the 1680-cm-1 band upon changes from K+ to Rb+ or Cs+ conditions. High-speed atomic force microscopy disclosed that TWIK1's surface morphology largely does not change in K+ and Na+ solutions. Our results reveal the local conformational changes of the TWIK1 selectivity filter and suggest that the amide-I bands may be useful "molecular fingerprints" for assessing the properties of other K+ channels.
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Affiliation(s)
- Hisao Tsukamoto
- From the Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, and.,Departments of Structural Molecular Science and
| | - Masahiro Higashi
- the Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213
| | - Hideyoshi Motoki
- the Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213
| | - Hiroki Watanabe
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Christian Ganser
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Koichi Nakajo
- the Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.,Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585
| | - Yoshihiro Kubo
- the Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.,Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585
| | - Takayuki Uchihashi
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Yuji Furutani
- From the Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, and .,Departments of Structural Molecular Science and
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13
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Katayama K, Furutani Y, Iwaki M, Fukuda T, Imai H, Kandori H. “In situ” observation of the role of chloride ion binding to monkey green sensitive visual pigment by ATR-FTIR spectroscopy. Phys Chem Chem Phys 2018; 20:3381-3387. [DOI: 10.1039/c7cp07277e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ATR-FTIR spectroscopic study elucidates the novel role of Cl−-binding in primate long-wavelength-sensitive (LWS) visual pigment.
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Affiliation(s)
- Kota Katayama
- Department of Life Science and Applied Chemistry
- Nagoya Institute of Technology
- Nagoya 466-8555
- Japan
| | - Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science
- Institute for Molecular Science
- Okazaki 444-8585
- Japan
| | - Masayo Iwaki
- Department of Life Science and Applied Chemistry
- Nagoya Institute of Technology
- Nagoya 466-8555
- Japan
| | - Tetsuya Fukuda
- Department of Life Science and Applied Chemistry
- Nagoya Institute of Technology
- Nagoya 466-8555
- Japan
| | - Hiroo Imai
- Primate Research Institute
- Kyoto University
- Inuyama 484-8506
- Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry
- Nagoya Institute of Technology
- Nagoya 466-8555
- Japan
- OptoBio Technology Research Center
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14
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Furutani Y. Ion-protein interactions of a potassium ion channel studied by attenuated total reflection Fourier transform infrared spectroscopy. Biophys Rev 2017; 10:235-239. [PMID: 29168118 DOI: 10.1007/s12551-017-0337-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/07/2017] [Indexed: 12/17/2022] Open
Abstract
An understanding of ion-protein interactions is key to a better understanding of the molecular mechanisms of proteins, such as enzymes, ion channels, and ion pumps. A potassium ion channel, KcsA, has been extensively studied in terms of ion selectivity. Alkali metal cations in the selectivity filter were visualized by X-ray crystallography. Infrared spectroscopy has an intrinsically higher structural sensitivity due to frequency changes in molecular vibrations interacting with different ions. In this review article, I attempt to summarize ion-exchange-induced differences in Fourier transform infrared spectroscopy, as applied to KcsA, to explain how this method can be utilized to study ion-protein interactions in the KcsA selectivity filter. A band at 1680 cm-1 in the amide I region would be a marker band for the ion occupancy of K+, Rb+, and Cs+ in the filter. The band at 1627 cm-1 observed in both Na+ and Li+ conditions suggests that the selectivity filter similarly interacts with these ions. In addition to the structural information, the results show that the titration of K+ ions provides quantitative information on the ion affinity of the selectivity filter.
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Affiliation(s)
- Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, 444-8585, Japan. .,Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, 240-0193, Japan.
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15
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Kasuya G, Fujiwara Y, Tsukamoto H, Morinaga S, Ryu S, Touhara K, Ishitani R, Furutani Y, Hattori M, Nureki O. Structural insights into the nucleotide base specificity of P2X receptors. Sci Rep 2017; 7:45208. [PMID: 28332633 PMCID: PMC5362899 DOI: 10.1038/srep45208] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 02/20/2017] [Indexed: 11/19/2022] Open
Abstract
P2X receptors are trimeric ATP-gated cation channels involved in diverse physiological processes, ranging from muscle contraction to nociception. Despite the recent structure determination of the ATP-bound P2X receptors, the molecular mechanism of the nucleotide base specificity has remained elusive. Here, we present the crystal structure of zebrafish P2X4 in complex with a weak affinity agonist, CTP, together with structure-based electrophysiological and spectroscopic analyses. The CTP-bound structure revealed a hydrogen bond, between the cytosine base and the side chain of the basic residue in the agonist binding site, which mediates the weak but significant affinity for CTP. The cytosine base is further recognized by two main chain atoms, as in the ATP-bound structure, but their bond lengths seem to be extended in the CTP-bound structure, also possibly contributing to the weaker affinity for CTP over ATP. This work provides the structural insights for the nucleotide base specificity of P2X receptors.
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Affiliation(s)
- Go Kasuya
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Yuichiro Fujiwara
- Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan
| | - Hisao Tsukamoto
- Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, 444-8585, Japan
| | - Satoshi Morinaga
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.,ERATO Touhara Chemosensory Signal Project, JST, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Satoshi Ryu
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.,ERATO Touhara Chemosensory Signal Project, JST, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Kazushige Touhara
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.,ERATO Touhara Chemosensory Signal Project, JST, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Ryuichiro Ishitani
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Yuji Furutani
- Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, 444-8585, Japan
| | - Motoyuki Hattori
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai, 200438, China
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
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16
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Joutsuka T, Morita A. Efficient Computation of Difference Vibrational Spectra in Isothermal–Isobaric Ensemble. J Phys Chem B 2016; 120:11229-11238. [DOI: 10.1021/acs.jpcb.6b07121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Tatsuya Joutsuka
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Akihiro Morita
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Elements
Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8520, Japan
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17
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Joutsuka T, Morita A. Improved Theory of Difference Vibrational Spectroscopy and Application to Water. J Chem Theory Comput 2016; 12:5026-5036. [DOI: 10.1021/acs.jctc.6b00697] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tatsuya Joutsuka
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Akihiro Morita
- Department
of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Elements
Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8520, Japan
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18
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Furutani Y, Shimizu H, Asai Y, Oiki S, Kandori H. Specific interactions between alkali metal cations and the KcsA channel studied using ATR-FTIR spectroscopy. Biophys Physicobiol 2015; 12:37-45. [PMID: 27493853 PMCID: PMC4736833 DOI: 10.2142/biophysico.12.0_37] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/21/2015] [Indexed: 01/20/2023] Open
Abstract
The X-ray structure of KcsA, a eubacterial potassium channel, displays a selectivity filter composed of four parallel peptide strands. The backbone carbonyl oxygen atoms of these strands solvate multiple K(+) ions. KcsA structures show different distributions of ions within the selectivity filter in solutions containing different cations. To assess the interactions of cations with the selectivity filter, we used attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Ion-exchange-induced ATR-FTIR difference spectra were obtained by subtracting the spectrum of KcsA soaked in K(+) solution from that obtained in Li(+), Na(+), Rb(+), and Cs(+) solutions. Large spectral changes in the amide-I and -II regions were observed upon replacing K(+) with smaller-sized cations Li(+) and Na(+) but not with larger-sized cations Rb(+) and Cs(+). These results strongly suggest that the selectivity filter carbonyls coordinating Rb(+) or Cs(+) adopt a conformation similar to those coordinating K(+) (cage configuration), but those coordinating Li(+) or Na(+) adopt a conformation (plane configuration) considerably different from those coordinating K(+). We have identified a cation-type sensitive amide-I band at 1681 cm(-1) and an insensitive amide-I band at 1659 cm(-1). The bands at 1650, 1639, and 1627 cm(-1) observed for Na(+)-coordinating carbonyls were almost identical to those observed in Li(+) solution, suggesting that KcsA forms a similar filter structure in Li(+) and Na(+) solutions. Thus, we conclude that the filter structure adopts a collapsed conformation in Li(+) solution that is similar to that in Na(+) solution but is in clear contrast to the X-ray crystal structure of KcsA with Li(+).
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Affiliation(s)
- Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan; Department of Frontier Materials, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Hirofumi Shimizu
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Matsuoka, Fukui 910-1193, Japan
| | - Yusuke Asai
- Department of Frontier Materials, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Matsuoka, Fukui 910-1193, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
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19
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Oiki S. Channel function reconstitution and re-animation: a single-channel strategy in the postcrystal age. J Physiol 2015; 593:2553-73. [PMID: 25833254 DOI: 10.1113/jp270025] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 03/24/2015] [Indexed: 01/30/2023] Open
Abstract
The most essential properties of ion channels for their physiologically relevant functions are ion-selective permeation and gating. Among the channel species, the potassium channel is primordial and the most ubiquitous in the biological world, and knowledge of this channel underlies the understanding of features of other ion channels. The strategy applied to studying channels changed dramatically after the crystal structure of the potassium channel was resolved. Given the abundant structural information available, we exploited the bacterial KcsA potassium channel as a simple model channel. In the postcrystal age, there are two effective frameworks with which to decipher the functional codes present in the channel structure, namely reconstitution and re-animation. Complex channel proteins are decomposed into essential functional components, and well-examined parts are rebuilt for integrating channel function in the membrane (reconstitution). Permeation and gating are dynamic operations, and one imagines the active channel by breathing life into the 'frozen' crystal (re-animation). Capturing the motion of channels at the single-molecule level is necessary to characterize the behaviour of functioning channels. Advanced techniques, including diffracted X-ray tracking, lipid bilayer methods and high-speed atomic force microscopy, have been used. Here, I present dynamic pictures of the KcsA potassium channel from the submolecular conformational changes to the supramolecular collective behaviour of channels in the membrane. These results form an integrated picture of the active channel and offer insights into the processes underlying the physiological function of the channel in the cell membrane.
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Affiliation(s)
- Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan
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20
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Stevenson P, Götz C, Baiz CR, Akerboom J, Tokmakoff A, Vaziri A. Visualizing KcsA conformational changes upon ion binding by infrared spectroscopy and atomistic modeling. J Phys Chem B 2015; 119:5824-31. [PMID: 25861001 PMCID: PMC4428008 DOI: 10.1021/acs.jpcb.5b02223] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effect of ion binding in the selectivity filter of the potassium channel KcsA is investigated by combining amide I Fourier-transform infrared spectroscopy with structure-based spectral modeling. Experimental difference IR spectra between K(+)-bound KcsA and Na(+)-bound KcsA are in good qualitative agreement with spectra modeled from structural ensembles generated from molecular dynamics simulations. The molecular origins of the vibrational modes contributing to differences in these spectra are determined not only from structural differences in the selectivity filter but also from the pore helices surrounding this region. Furthermore, the coordination of K(+) or Na(+) to carbonyls in the selectivity filter effectively decouples the vibrations of those carbonyls from the rest of the protein, creating local probes of the electrostatic environment. The results suggest that it is necessary to include the influence of the surrounding helices in discussing selectivity and transport in KcsA and, on a more general level, that IR spectroscopy offers a nonperturbative route to studying the structure and dynamics of ion channels.
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Affiliation(s)
- Paul Stevenson
- †Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States.,‡Department of Chemistry, James Frank Institute, and The Institute for Biophysical Dynamics, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States
| | - Christoph Götz
- §Research Institute of Molecular Pathology (IMP), Dr Bohr-Gasse 7, A-1030 Wien, Austria
| | - Carlos R Baiz
- ‡Department of Chemistry, James Frank Institute, and The Institute for Biophysical Dynamics, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States
| | | | - Andrei Tokmakoff
- ‡Department of Chemistry, James Frank Institute, and The Institute for Biophysical Dynamics, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States
| | - Alipasha Vaziri
- §Research Institute of Molecular Pathology (IMP), Dr Bohr-Gasse 7, A-1030 Wien, Austria
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21
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Inokuchi Y, Ebata T, Ikeda T, Haino T, Kimura T, Guo H, Furutani Y. New insights into metal ion–crown ether complexes revealed by SEIRA spectroscopy. NEW J CHEM 2015. [DOI: 10.1039/c5nj01787d] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate the SEIRA spectroscopy of crown ether complexes for examining the relationship between the guest selectivity, structure, and solvent effect.
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Affiliation(s)
- Yoshiya Inokuchi
- Department of Chemistry
- Graduate School of Science
- Hiroshima University
- Higashi-Hiroshima
- Hiroshima 739-8526
| | - Takayuki Ebata
- Department of Chemistry
- Graduate School of Science
- Hiroshima University
- Higashi-Hiroshima
- Hiroshima 739-8526
| | - Toshiaki Ikeda
- Department of Chemistry
- Graduate School of Science
- Hiroshima University
- Higashi-Hiroshima
- Hiroshima 739-8526
| | - Takeharu Haino
- Department of Chemistry
- Graduate School of Science
- Hiroshima University
- Higashi-Hiroshima
- Hiroshima 739-8526
| | | | - Hao Guo
- Institute for Molecular Science
- Myodaiji
- Japan
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22
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Yamakata A, Shimizu H, Oiki S. Surface-enhanced IR absorption spectroscopy of the KcsA potassium channel upon application of an electric field. Phys Chem Chem Phys 2015; 17:21104-11. [DOI: 10.1039/c5cp02681d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Surface-enhanced IR absorption spectroscopy coupled with an electrochemical system enables the potassium-induced specific structural change of the potassium channel.
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Affiliation(s)
- Akira Yamakata
- Graduate School of Engineering
- Toyota Technological Institute
- Tempaku
- Japan
| | - Hirofumi Shimizu
- Department of Molecular Physiology and Biophysics
- Faculty of Medical Sciences
- University of Fukui
- Fukui 910-1193
- Japan
| | - Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics
- Faculty of Medical Sciences
- University of Fukui
- Fukui 910-1193
- Japan
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23
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Kandori H, Furutani Y, Murata T. Infrared spectroscopic studies on the V-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:134-41. [PMID: 25111748 DOI: 10.1016/j.bbabio.2014.07.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 11/27/2022]
Abstract
V-ATPase is an ATP-driven rotary motor that vectorially transports ions. Together with F-ATPase, a homologous protein, several models on the ion transport have been proposed, but their molecular mechanisms are yet unknown. V-ATPase from Enterococcus hirae forms a large supramolecular protein complex (total molecular weight: ~700,000) and physiologically transports Na⁺ and Li⁺ across a hydrophobic lipid bilayer. Stabilization of these cations in the binding site has been discussed on the basis of X-ray crystal structures of a membrane-embedded domain, the K-ring (Na⁺ and Li⁺ bound forms). Sodium or lithium ion binding-induced difference FTIR spectra of the intact E. hirae V-ATPase have been measured in aqueous solution at physiological temperature. The results suggest that sodium or lithium ion binding induces the deprotonation of Glu139, a hydrogen-bonding change in the tyrosine residue and rigid α-helical structures. Identical difference FTIR spectra between the entire V-ATPase complex and K-ring strongly suggest that protein interaction with the I subunit does not cause large structural changes in the K-ring. This result supports the previously proposed Na⁺ transport mechanism by V-ATPase stating that a flip-flop movement of a carboxylate group of Glu139 without large conformational changes in the K-ring accelerates the replacement of a Na⁺ ion in the binding site. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.
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Affiliation(s)
- Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
| | - Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan; Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Takeshi Murata
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan; Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
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24
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Sakaguchi S, Ishiyama T, Morita A. Theory and efficient computation of differential vibrational spectra. J Chem Phys 2014; 140:144109. [DOI: 10.1063/1.4870523] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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25
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Phongphanphanee S, Yoshida N, Oiki S, Hirata F. Probing “ambivalent” snug-fit sites in the KcsA potassium channel using three-dimensional reference interaction site model (3D-RISM) theory. PURE APPL CHEM 2014. [DOI: 10.1515/pac-2014-5018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The potassium channel is highly selective for K+ over Na+, and the mechanism underlying this selectivity remains unclear. We show the three-dimensional distribution functions (3D-DFs) of small cations (Li+, Na+, and K+) and the free energy profile of ions inside the open selectivity filter (SF) of the KcsA channel. Our previous results [S. Phongphanphanee, N. Yoshida, S. Oiki, F. Hirata. Abstract Book of 5th International Symposium on Molecular Science of Fluctuations toward Biological Functions, P062 (2012)] indicate that the 3D-DF for K+ exhibits distinct peaks at the sites formed by the eight carbonyl oxygen atoms belonging to the surrounding peptide-backbone and residues (the cage site). Li+ has sharp distributions in the 3D-DF at the center of a quadruplex composed of four carbonyl oxygen atoms (the plane site). Na+ has a rather diffuse distribution throughout the SF region with peaks both in the plane and in cage sites. The results provide microscopic evidence of the phenomenological findings that Li+ and Na+ are not excluded from the SF region and that the binding affinity alone does not cause the ion selectivity of KcsA. In the present study, with an ion placed explicitly along the pore axis, the free energy profiles of the ions inside the SF were calculated; from these profiles we suggest a new mechanism for selective K+ permeation. According to the model, a K+ ion must overcome a free energy barrier that is approximately half that of Na+ to exit from either of the SF mouths due to the existence of an intermediate local minimum along the route for climbing the barriers.
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26
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Inokuchi Y, Mizuuchi T, Ebata T, Ikeda T, Haino T, Kimura T, Guo H, Furutani Y. Formation of host–guest complexes on gold surface investigated by surface-enhanced IR absorption spectroscopy. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2013.12.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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27
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Fukuda T, Muroda K, Kandori H. Detection of a protein-bound water vibration of halorhodopsin in aqueous solution. Biophysics (Nagoya-shi) 2013; 9:167-72. [PMID: 27493555 PMCID: PMC4629683 DOI: 10.2142/biophysics.9.167] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/04/2013] [Indexed: 01/14/2023] Open
Abstract
Protein-bound water molecules play crucial roles in their structure and function, but their detection is an experimental challenge, particularly in aqueous solution at room temperature. By applying attenuated total reflection (ATR) Fourier-transform infrared (FTIR) spectroscopy to a light-driven Cl(-) pump pharaonis halorhodopsin (pHR), here we detected an O-H stretching vibration of protein-bound water molecules in the active center. The pHR(Cl(-)) minus pHR(Br(-)) ATR-FTIR spectra show random fluctuation at 3600-3000 cm(-1), frequency window of water vibration, which can be interpreted in terms of dynamical fluctuation of aqueous water at room temperature. On the other hand, we observed a reproducible spectral feature at 3617 (+)/3630 (-) cm(-1) in the pHR(Cl(-)) minus pHR(Br(-)) spectrum, which is absent in the pHR(Cl(-)) minus pHR(Cl(-)) and in the pHR(Br(-)) minus pHR(Br(-)) spectra. The water O-H stretching vibrations of pHR(Cl(-)) and pHR(Br(-)) at 3617 and 3630 cm(-1), respectively, are confirmed by light-induced difference FTIR spectra in isotope water (H2 (18)O) at 77 K. The observed water molecule presumably binds to the active center of pHR, and alter its hydrogen bond during the Cl(-) pumping photocycle.
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Affiliation(s)
- Tetsuya Fukuda
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Kosuke Muroda
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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28
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Structural changes of the KcsA potassium channel upon application of the electrode potential studied by surface-enhanced IR absorption spectroscopy. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.02.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Maréchal A, Iwaki M, Rich PR. Structural Changes in Cytochrome c Oxidase Induced by Binding of Sodium and Calcium Ions: An ATR-FTIR Study. J Am Chem Soc 2013; 135:5802-7. [DOI: 10.1021/ja4005706] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Amandine Maréchal
- Glynn Laboratory of
Bioenergetics,
Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, United
Kingdom
| | - Masayo Iwaki
- Glynn Laboratory of
Bioenergetics,
Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, United
Kingdom
| | - Peter R. Rich
- Glynn Laboratory of
Bioenergetics,
Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, United
Kingdom
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