1
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Wang X, Yu B, Iwahara J. Slow Rotational Dynamics of Cytosine NH 2 Groups in Double-Stranded DNA. Biochemistry 2022; 61:1415-1418. [PMID: 35759792 PMCID: PMC9805297 DOI: 10.1021/acs.biochem.2c00299] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Aromatic NH2 groups are essential as hydrogen-bond donors in secondary structures of DNA and RNA. Although rapid rotations of NH2 groups of adenine and guanine bases were previously characterized, there has been a lack of quantitative information about slow rotations of cytosine NH2 groups in Watson-Crick base pairs. In this study, using an NMR method we had recently developed, we determined the kinetic rate constants and energy barriers for cytosine NH2 rotations in a 15-base-pair DNA duplex. Our data show that the rotational dynamics of cytosine NH2 groups depend on local environments. Qualitative correlation between the ranges of 15N chemical shifts and rotational time scales for various NH2 groups of nucleic acids and proteins illuminates a relationship between the partial double-bond character of the C-N bond and the time scale for NH2 rotations.
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2
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Abstract
Thanks to recent improvements in NMR spectrometer hardware and pulse sequence design, modern 13C NMR has become a useful tool for biomolecular applications. The complete assignment of a protein can be accomplished by using 13C detected multinuclear experiments and it can provide unique information relevant for the study of a variety of different biomolecules including paramagnetic proteins and intrinsically disordered proteins. A wide range of NMR observables can be measured, concurring to the structural and dynamic characterization of a protein in isolation, as part of a larger complex, or even inside a living cell. We present the different properties of 13C with respect to 1H, which provide the rationale for the experiments developed and their application, the technical aspects that need to be faced, and the many experimental variants designed to address different cases. Application areas where these experiments successfully complement proton NMR are also described.
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Affiliation(s)
- Isabella C. Felli
- Department of Chemistry “Ugo
Schiff” and Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino (Florence), Italy
| | - Roberta Pierattelli
- Department of Chemistry “Ugo
Schiff” and Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino (Florence), Italy
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3
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Singh R, Kumar P, Sindhu J, Devi M. Synthesis and exploration of configurational dynamics in equilibrating E/ Z 2-aryliminothiazolidin-4-ones using NMR and estimation of thermodynamic parameters. NEW J CHEM 2022. [DOI: 10.1039/d1nj06109g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
NMR based in-depth exploration of stereodynamic behavior in equilibrating E/Z 2-aryliminothiazolidin-4-ones and determination of kinetic and thermodynamic parameters.
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Affiliation(s)
- Rahul Singh
- Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India
| | - Parvin Kumar
- Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India
| | - Jayant Sindhu
- Department of Chemistry, COBS&H, CCS Haryana Agricultural University, Hisar-125004, India
| | - Meena Devi
- Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India
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4
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Wang X, Yu B, Iwahara J. Hindered Rotations of Protein Asparagine/Glutamine Side-Chain NH 2 Groups: Impact of Hydrogen Bonding with DNA. J Phys Chem Lett 2021; 12:11378-11382. [PMID: 34784468 PMCID: PMC8643942 DOI: 10.1021/acs.jpclett.1c03467] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Hindered rotation about an sp2 C-N bond is known to occur in arginine (Arg), asparagine (Asn), and glutamine (Gln) side chains of proteins. However, very little is known about the rotational dynamics of Asn and Gln side-chain NH2 groups. Here, using a unique NMR method, we quantitatively characterized the hindered rotations of protein Asn/Gln side-chain NH2 groups. This NMR method yields simple NH2-selective spectra that allow for an accurate determination of the kinetic rate constants for the hindered rotations. Through the NMR measurements at different temperatures, we investigated the energy barriers that restrict the C-N bond rotations of protein side-chain NH2 groups. Through a comparison of the kinetic data for the free and DNA-bound states of the Antp homeodomain, we also examined the impact of hydrogen bonding on the hindered rotations of the side-chain NH2 groups. Our data suggest that the hydrogen bonding increases the energy barriers by 1-6 kJ/mol.
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Affiliation(s)
- Xi Wang
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Binhan Yu
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas 77555, United States
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5
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Karunanithy G, Reinstein J, Hansen DF. Multiquantum Chemical Exchange Saturation Transfer NMR to Quantify Symmetrical Exchange: Application to Rotational Dynamics of the Guanidinium Group in Arginine Side Chains. J Phys Chem Lett 2020; 11:5649-5654. [PMID: 32543198 PMCID: PMC7370295 DOI: 10.1021/acs.jpclett.0c01322] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Chemical exchange saturation transfer (CEST) NMR experiments have emerged as a powerful tool for characterizing dynamics in proteins. We show here that the CEST approach can be extended to systems with symmetrical exchange, where the NMR signals of all exchanging species are severely broadened. To achieve this, multiquantum CEST (MQ-CEST) is introduced, where the CEST pulse is applied to a longitudinal multispin order density element and the CEST profiles are encoded onto nonbroadened nuclei. The MQ-CEST approach is demonstrated on the restricted rotation of guanidinium groups in arginine residues within proteins. These groups and their dynamics are essential for many enzymes and for noncovalent interactions through the formation of hydrogen bonds, salt-bridges, and π-stacking interactions, and their rate of rotation is highly indicative of the extent of interactions formed. The MQ-CEST method is successfully applied to guanidinium groups in the 19 kDa L99A mutant of T4 lysozyme.
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Affiliation(s)
- Gogulan Karunanithy
- Institute
of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
| | - Jochen Reinstein
- Department
of Biomolecular Mechanisms, Max Planck Institute
for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Germany
| | - D. Flemming Hansen
- Institute
of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
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6
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Lu J, Zhou F, Liu W, Yu F. Mass spectrometry assisted arginine side chains assignment of NMR resonances in natural abundance proteins. JOURNAL OF BIOMOLECULAR NMR 2020; 74:173-181. [PMID: 32008172 DOI: 10.1007/s10858-020-00302-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/27/2020] [Indexed: 06/10/2023]
Abstract
Arginine side chains play critical roles in many protein-ligand interactions and enzyme catalysis. Unambiguous resonance assignment is a prerequisite for the nuclear magnetic resonance (NMR) spectroscopy studies of arginine side chains dynamics and hydrogen exchange properties from which one can expect to elucidate in more detail the roles of arginine residues in protein structure and function. Here we present a new mass spectrometry (MS)-based method for assigning the side-chain resonances of arginine residues in 2D 1H-15N NMR spectra. The method requires no additional isotopic labeling, and relies on knowledge of the amino acid sequence, the modification of the guanidino groups and liquid chromatography-mass spectrometry rather than the protein's structure or properties. Correlating the modification rates can connect cross-peak positions from NMR data with MS data to support resonances assignments. In the present work, we have extended our original application to natural abundance human ubiquitin to provide ε-NH assessments of three arginine for this well-studied protein.
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Affiliation(s)
- Jingjing Lu
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, Yantai, China
- State Key Laboratory of Long-Acting and Targeting Drug Delivery Technologies, Shandong Luye Pharmaceutical Co. Ltd., Yantai, China
| | - Fengmei Zhou
- State Key Laboratory of Long-Acting and Targeting Drug Delivery Technologies, Shandong Luye Pharmaceutical Co. Ltd., Yantai, China
| | - Wanhui Liu
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, Yantai, China
| | - Fei Yu
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, Yantai, China.
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7
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Craig HC, Blamires SJ, Sani MA, Kasumovic MM, Rawal A, Hook JM. DNP NMR spectroscopy reveals new structures, residues and interactions in wild spider silks. Chem Commun (Camb) 2019; 55:4687-4690. [PMID: 30938741 DOI: 10.1039/c9cc01045a] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
DNP solid state NMR spectroscopy allows non-targeted analysis of wild spider silk in unprecedented detail at natural abundance, revealing hitherto unreported features across several species. A >50-fold signal enhancement for each silk, enables the detection of novel H-bonding networks and arginine conformations, and the post-translational modified amino acid, hydroxyproline.
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Affiliation(s)
- Hamish C Craig
- School of Biological, Earth and Environmental Science, University of New South Wales, Sydney, 2052, Australia.
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8
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Pritchard RB, Hansen DF. Characterising side chains in large proteins by protonless 13C-detected NMR spectroscopy. Nat Commun 2019; 10:1747. [PMID: 30988305 PMCID: PMC6465260 DOI: 10.1038/s41467-019-09743-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/28/2019] [Indexed: 11/24/2022] Open
Abstract
Side chains cover protein surfaces and are fundamental to processes as diverse as substrate recognition, protein folding and enzyme catalysis. However, characterisation of side-chain motions has so far been restricted to small proteins and methyl-bearing side chains. Here we present a class of methods, based on 13C-detected NMR spectroscopy, to more generally quantify motions and interactions of side chains in medium-to-large proteins. A single, uniformly isotopically labelled sample is sufficient to characterise the side chains of six different amino acid types. Side-chain conformational dynamics on the millisecond time-scale can be quantified by incorporating chemical exchange saturation transfer (CEST) into the presented methods, whilst long-range 13C-13C scalar couplings reporting on nanosecond to millisecond motions can be quantified in proteins as large as 80 kDa. The presented class of methods promises characterisation of side-chain behaviour at a level that has so far been reserved for the protein backbone. Analysis of side-chain motions by NMR has so far been restricted to small proteins and methyl-bearing side chains. Here, the authors present NMR methods based on 13C direct detection of highly deuterated protein samples that yield sharp and well-resolved signals and allow the characterisation of side-chain conformational dynamics of six different amino acid types in medium-to-large proteins.
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Affiliation(s)
- Ruth B Pritchard
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK, WC1E 6BT
| | - D Flemming Hansen
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK, WC1E 6BT.
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9
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Batchelor M, Wolny M, Baker EG, Paci E, Kalverda AP, Peckham M. Dynamic ion pair behavior stabilizes single α-helices in proteins. J Biol Chem 2019; 294:3219-3234. [PMID: 30593502 PMCID: PMC6398138 DOI: 10.1074/jbc.ra118.006752] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/17/2018] [Indexed: 11/06/2022] Open
Abstract
Ion pairs are key stabilizing interactions between oppositely charged amino acid side chains in proteins. They are often depicted as single conformer salt bridges (hydrogen-bonded ion pairs) in crystal structures, but it is unclear how dynamic they are in solution. Ion pairs are thought to be particularly important in stabilizing single α-helix (SAH) domains in solution. These highly stable domains are rich in charged residues (such as Arg, Lys, and Glu) with potential ion pairs across adjacent turns of the helix. They provide a good model system to investigate how ion pairs can contribute to protein stability. Using NMR spectroscopy, small-angle X-ray light scattering (SAXS), and molecular dynamics simulations, we provide here experimental evidence that ion pairs exist in a SAH in murine myosin 7a (residues 858-935), but that they are not fixed or long lasting. In silico modeling revealed that the ion pairs within this α-helix exhibit dynamic behavior, rapidly forming and breaking and alternating between different partner residues. The low-energy helical state was compatible with a great variety of ion pair combinations. Flexible ion pair formation utilizing a subset of those available at any one time avoided the entropic penalty of fixing side chain conformations, which likely contributed to helix stability overall. These results indicate the dynamic nature of ion pairs in SAHs. More broadly, thermodynamic stability in other proteins is likely to benefit from the dynamic behavior of multi-option solvent-exposed ion pairs.
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Affiliation(s)
- Matthew Batchelor
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Marcin Wolny
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Emily G Baker
- the School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Emanuele Paci
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Arnout P Kalverda
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Michelle Peckham
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
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10
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Mackenzie HW, Hansen DF. Arginine Side-Chain Hydrogen Exchange: Quantifying Arginine Side-Chain Interactions in Solution. Chemphyschem 2019; 20:252-259. [PMID: 30085401 PMCID: PMC6391956 DOI: 10.1002/cphc.201800598] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Indexed: 02/03/2023]
Abstract
The rate with which labile backbone hydrogen atoms in proteins exchange with the solvent has long been used to probe protein interactions in aqueous solutions. Arginine, an essential amino acid found in many interaction interfaces, is capable of an impressive range of interactions via its guanidinium group. The hydrogen exchange rate of the guanidinium hydrogens therefore becomes an important measure to quantify side-chain interactions. Herein we present an NMR method to quantify the hydrogen exchange rates of arginine side-chain 1 Hϵ protons and thus present a method to gauge the strength of arginine side-chain interactions. The method employs 13 C-detection and the one-bond deuterium isotope shift observed for 15 Nϵ to generate two exchanging species in 1 H2 O/2 H2 O mixtures. An application to the protein T4 Lysozyme is shown, where protection factors calculated from the obtained exchange rates correlate well with the interactions observed in the crystal structure. The methodology presented provides an important step towards characterising interactions of arginine side-chains in enzymes, in phase separation, and in protein interaction interfaces in general.
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Affiliation(s)
- Harold W. Mackenzie
- Institute of Structural and Molecular Biology Division of BiosciencesUniversity College LondonLondon WC1E 6BTUnited Kingdom
| | - D. Flemming Hansen
- Institute of Structural and Molecular Biology Division of BiosciencesUniversity College LondonLondon WC1E 6BTUnited Kingdom
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11
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Brockerman JA, Okon M, Withers SG, McIntosh LP. The pK a values of the catalytic residues in the retaining glycoside hydrolase T26H mutant of T4 lysozyme. Protein Sci 2018; 28:620-632. [PMID: 30537432 DOI: 10.1002/pro.3562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 11/29/2018] [Accepted: 12/03/2018] [Indexed: 12/24/2022]
Abstract
T4 phage lysozyme (T4L) is an enzyme that cleaves bacterial cell wall peptidoglycan. Remarkably, the single substitution of the active site Thr26 to a His (T26H) converts T4L from an inverting to a retaining glycoside hydrolase with transglycosylase activity. It has been proposed that T26H-T4L follows a double displacement mechanism with His26 serving as a nucleophile to form a covalent glycosyl-enzyme intermediate (Kuroki et al., PNAS 1999; 96:8949-8954). To gain further insights into this or alternative mechanisms, we used NMR spectroscopy to measure the acid dissociation constants (pKa values) and/or define the ionization states of the Asp, Glu, His, and Arg residues in the T4L mutant. Most notably, the pKa value of the putative nucleophile His26 is 6.8 ± 0.1, whereas that of the general acid Glu11 is 4.7 ± 0.1. If the proposed mechanism holds true, then T26H-T4L follows a reverse protonation pathway in which only a minor population of the free enzyme is in its catalytically competent ionization state with His26 deprotonated and Glu11 protonated. Our studies also confirm that all arginines in T26H-T4L, including the active site Arg145, are positively charged under neutral pH conditions. BRIEF STATEMENT: The replacement of a single amino acid changes T4 lysozyme from an inverting to a retaining glycoside hydrolase. Using NMR spectroscopy, we measured the pKa values of the ionizable residues in the active site of this mutant enzyme. Along with previously reported data, these results provide important constraints for understanding the catalytic mechanisms by which the wild-type and mutant form of T4 lysozyme cleave bacterial peptidoglycan.
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Affiliation(s)
- Jacob A Brockerman
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.,Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Stephen G Withers
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.,Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada.,Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.,Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada.,Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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12
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Nguyen D, Chen C, Pettitt BM, Iwahara J. NMR Methods for Characterizing the Basic Side Chains of Proteins: Electrostatic Interactions, Hydrogen Bonds, and Conformational Dynamics. Methods Enzymol 2018; 615:285-332. [PMID: 30638532 DOI: 10.1016/bs.mie.2018.08.017] [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] [Indexed: 01/09/2023]
Abstract
NMR spectroscopy is a powerful tool for studying protein dynamics. Conventionally, NMR studies on protein dynamics have probed motions of protein backbone NH, side-chain aromatic, and CH3 groups. Recently, there has been remarkable progress in NMR methodologies that can characterize motions of cationic groups in protein side chains. These NMR methods allow investigations of the dynamics of positively charged lysine (Lys) and arginine (Arg) side chains and their hydrogen bonds as well as their electrostatic interactions important for protein function. Here, describing various practical aspects, we provide an overview of the NMR methods for dynamics studies of Lys and Arg side chains. Some example data on protein-DNA complexes are shown. We will also explain how molecular dynamics (MD) simulations can facilitate the interpretation of the NMR data on these basic side chains. Studies combining NMR and MD have revealed the highly dynamic nature of short-range electrostatic interactions via ion pairs, especially those involving Lys side chains.
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Affiliation(s)
- Dan Nguyen
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
| | - Chuanying Chen
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
| | - B Montgomery Pettitt
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States.
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13
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Nguyen D, Iwahara J. Impact of two-bond 15N- 15N scalar couplings on 15N transverse relaxation measurements for arginine side chains of proteins. JOURNAL OF BIOMOLECULAR NMR 2018; 71:45-51. [PMID: 29845493 PMCID: PMC6020141 DOI: 10.1007/s10858-018-0189-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 05/23/2018] [Indexed: 06/08/2023]
Abstract
NMR relaxation of arginine (Arg) 15Nε nuclei is useful for studying side-chain dynamics of proteins. In this work, we studied the impact of two geminal 15N-15N scalar couplings on measurements of transverse relaxation rates (R 2 ) for Arg side-chain 15Nε nuclei. For 12 Arg side chains of the DNA-binding domain of the Antp protein, we measured the geminal 15N-15N couplings ( 2 J NN ) of the 15Nε nuclei and found that the magnitudes of the 2 J NN coupling constants were virtually uniform with an average of 1.2 Hz. Our simulations, assuming ideal 180° rotations for all 15N nuclei, suggested that the two 2 J NN couplings of this magnitude could in principle cause significant modulation in signal intensities during the Carr-Purcell-Meiboom-Gill (CPMG) scheme for Arg 15Nε R 2 measurements. However, our experimental data show that the expected modulation via two 2 J NN couplings vanishes during the 15N CPMG scheme. This quenching of J modulation can be explained by the mechanism described in Dittmer and Bodenhausen (Chemphyschem 7:831-836, 2006). This effect allows for accurate measurements of R 2 relaxation rates for Arg side-chain 15Nε nuclei despite the presence of two 2 J NN couplings. Although the so-called recoupling conditions may cause overestimate of R 2 rates for very mobile Arg side chains, such conditions can readily be avoided through appropriate experimental settings.
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Affiliation(s)
- Dan Nguyen
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, 77555-1068, USA
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, 77555-1068, USA.
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14
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Mackenzie HW, Hansen DF. A 13C-detected 15N double-quantum NMR experiment to probe arginine side-chain guanidinium 15N η chemical shifts. JOURNAL OF BIOMOLECULAR NMR 2017; 69:123-132. [PMID: 29127559 PMCID: PMC5711973 DOI: 10.1007/s10858-017-0137-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 09/25/2017] [Indexed: 05/25/2023]
Abstract
Arginine side-chains are often key for enzyme catalysis, protein-ligand and protein-protein interactions. The importance of arginine stems from the ability of the terminal guanidinium group to form many key interactions, such as hydrogen bonds and salt bridges, as well as its perpetual positive charge. We present here an arginine 13Cζ-detected NMR experiment in which a double-quantum coherence involving the two 15Nη nuclei is evolved during the indirect chemical shift evolution period. As the precession frequency of the double-quantum coherence is insensitive to exchange of the two 15Nη; this new approach is shown to eliminate the previously deleterious line broadenings of 15Nη resonances caused by the partially restricted rotation about the Cζ-Nε bond. Consequently, sharp and well-resolved 15Nη resonances can be observed. The utility of the presented method is demonstrated on the L99A mutant of the 19 kDa protein T4 lysozyme, where the measurement of small chemical shift perturbations, such as one-bond deuterium isotope shifts, of the arginine amine 15Nη nuclei becomes possible using the double-quantum experiment.
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Affiliation(s)
- Harold W Mackenzie
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - D Flemming Hansen
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK.
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