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Yu B, Bolik-Coulon N, Rangadurai AK, Kay LE, Iwahara J. Gadolinium-Based NMR Spin Relaxation Measurements of Near-Surface Electrostatic Potentials of Biomolecules. J Am Chem Soc 2024; 146:20788-20801. [PMID: 39028837 PMCID: PMC11295196 DOI: 10.1021/jacs.4c04433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 06/09/2024] [Accepted: 06/28/2024] [Indexed: 07/21/2024]
Abstract
NMR spectroscopy is an important tool for the measurement of the electrostatic properties of biomolecules. To this point, paramagnetic relaxation enhancements (PREs) of 1H nuclei arising from nitroxide cosolutes in biomolecular solutions have been used to measure effective near-surface electrostatic potentials (ϕENS) of proteins and nucleic acids. Here, we present a gadolinium (Gd)-based NMR method, exploiting Gd chelates with different net charges, for measuring ϕENS values and demonstrate its utility through applications to a number of biomolecular systems. The use of Gd-based cosolutes offers several advantages over nitroxides for ϕENS measurements. First, unlike nitroxide compounds, Gd chelates enable electrostatic potential measurements on oxidation-sensitive proteins that require reducing agents. Second, the large electron spin quantum number of Gd (7/2) results in notably larger PREs for Gd chelates when used at the same concentrations as nitroxide radicals. Thus, it is possible to measure ϕENS values exclusively from + and - charged compounds even for highly charged biomolecules, avoiding the use of neutral cosolutes that, as we further establish here, limits the accuracy of the measured electrostatic potentials. In addition, the smaller concentrations of cosolutes required minimize potential binding to sites on macromolecules. Fourth, the closer proximity of the paramagnetic center and charged groups within Gd chelates, in comparison to the corresponding nitroxide compounds, enables more accurate predictions of ϕENS potentials for cross-validation of the experimental results. The Gd-based method described here, thus, broadens the applicability of studies of biomolecular electrostatics using solution NMR spectroscopy.
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Affiliation(s)
- Binhan Yu
- Department
of Biochemistry & Molecular Biology, Sealy Center for Structural
Biology & Molecular Biophysics, University
of Texas Medical Branch, Galveston, Texas 77555-1068, United States
| | - Nicolas Bolik-Coulon
- Department
of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department
of Biochemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Atul K. Rangadurai
- Department
of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department
of Biochemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Program
in Molecular Medicine, Hospital for Sick
Children Research Institute, Toronto, Ontario M5G 0A4, Canada
| | - Lewis E. Kay
- Department
of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department
of Biochemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Program
in Molecular Medicine, Hospital for Sick
Children Research Institute, Toronto, Ontario M5G 0A4, Canada
| | - Junji Iwahara
- Department
of Biochemistry & Molecular Biology, Sealy Center for Structural
Biology & Molecular Biophysics, University
of Texas Medical Branch, Galveston, Texas 77555-1068, United States
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Yu B, Wang X, Wang T, Iwahara J. DNA base order parameter determination without influence of chemical exchange. Methods 2023; 210:1-9. [PMID: 36596431 PMCID: PMC9898221 DOI: 10.1016/j.ymeth.2022.12.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 12/23/2022] [Accepted: 12/30/2022] [Indexed: 01/01/2023] Open
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is a versatile tool used to investigate the dynamic properties of biological macromolecules and their complexes. NMR relaxation data can provide order parameters S2, which represent the mobility of bond vectors reorienting within a molecular frame. Determination of S2 parameters typically involves the use of transverse NMR relaxation rates. However, the accuracy in S2 determination can be diminished by elevation of the transverse relaxation rates through conformational or chemical exchange involving protonation/deprotonation or non-Watson-Crick base-pair states of nucleic acids. Here, we propose an approach for determination of S2 parameters without the influence of exchange processes. This approach utilizes transverse and longitudinal 13C chemical shift anisotropy (CSA) - dipole-dipole (DD) cross-correlation rates instead of 13C transverse relaxation rates. Anisotropy in rotational diffusion is taken into consideration. An application of this approach to nucleotide base CH groups of a uniformly 13C/15N-labeled DNA duplex is demonstrated.
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Affiliation(s)
- Binhan Yu
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Xi Wang
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Tianzhi Wang
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Junji Iwahara
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
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3
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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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Nepravishta R, Pletka CC, Iwahara J. Racemic phosphorothioate as a tool for NMR investigations of protein-DNA complexes. JOURNAL OF BIOMOLECULAR NMR 2020; 74:421-429. [PMID: 32683519 PMCID: PMC7511421 DOI: 10.1007/s10858-020-00333-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 07/09/2020] [Indexed: 05/05/2023]
Abstract
A major driving force for protein-nucleic acid association is electrostatic interactions via ion pairs of the positively charged basic side chains and negatively charged phosphates. For a better understanding of how proteins scan DNA and recognize particular signatures, it is important to gain atomic-level insight into the behavior of basic side chains at the protein-DNA interfaces. NMR spectroscopy is a powerful tool for investigating the structural, dynamic, and kinetic aspects of protein-DNA interactions. However, resonance assignment of basic side-chain cationic moieties at the molecular interfaces remains to be a major challenge. Here, we propose a fast, robust, and inexpensive approach that greatly facilitates resonance assignment of interfacial moieties and also allows for kinetic measurements of protein translocation between two DNA duplexes. This approach utilizes site-specific incorporation of racemic phosphorothioate at the position of a phosphate that interacts with a protein side chain. This modification retains the electric charge of phosphate and therefore is mild, but causes significant chemical shift perturbations for the proximal protein side chains, which facilitates resonance assignment. Due to the racemic nature of the modification, two different chemical shifts are observed for the species with different diastereomers RP and SP of the incorporated phosphorothioate group. Kinetic information on the exchange of the protein molecule between RP and SP DNA duplexes can be obtained by 15Nz exchange spectroscopy. We demonstrate the applications of this approach to the Antennapedia homeodomain-DNA complex and the CREB1 basic leucine-zipper (bZIP)-DNA complex.
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Affiliation(s)
- Ridvan Nepravishta
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, 77555-1068, USA
| | - Channing C Pletka
- 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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5
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Nguyen D, Hoffpauir ZA, Iwahara J. Internal Motions of Basic Side Chains of the Antennapedia Homeodomain in the Free and DNA-Bound States. Biochemistry 2017; 56:5866-5869. [PMID: 29045141 PMCID: PMC5682595 DOI: 10.1021/acs.biochem.7b00885] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Basic side chains play crucial roles in protein-DNA interactions. In this study, using NMR spectroscopy, we investigated the dynamics of Arg and Lys side chains of the fruit fly Antennapedia homeodomain in the free state and in the complex with target DNA. We measured 15N relaxation for Arg and Lys side chains at two magnetic fields, from which generalized order parameters for the cationic groups were determined. Mobility of the R5 side chain, which makes hydrogen bonds with a thymine base in the DNA minor groove, was greatly dampened. Several Lys and Arg side chains that form intermolecular ion pairs with DNA phosphates were found to retain high mobility with the order parameter being <0.6 in the DNA-bound state. Interestingly, some of the interfacial cationic groups in the complex were more mobile than in the free protein. The retained or enhanced mobility of the Arg and Lys side chains in the complex should mitigate the overall loss of conformational entropy in the protein-DNA association and allow dynamic molecular recognition.
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Affiliation(s)
- Dan Nguyen
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Zoe A. Hoffpauir
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Junji Iwahara
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
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Zandarashvili L, Nguyen D, Anderson KM, White MA, Gorenstein DG, Iwahara J. Entropic Enhancement of Protein-DNA Affinity by Oxygen-to-Sulfur Substitution in DNA Phosphate. Biophys J 2016; 109:1026-37. [PMID: 26331260 DOI: 10.1016/j.bpj.2015.07.032] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 07/07/2015] [Accepted: 07/15/2015] [Indexed: 10/23/2022] Open
Abstract
Dithioation of DNA phosphate is known to enhance binding affinities, at least for some proteins. We mechanistically characterized this phenomenon for the Antennapedia homeodomain-DNA complex by integrated use of fluorescence, isothermal titration calorimetry, NMR spectroscopy, and x-ray crystallography. By fluorescence and isothermal titration calorimetry, we found that this affinity enhancement is entropy driven. By NMR, we investigated the ionic hydrogen bonds and internal motions of lysine side-chain NH3(+) groups involved in ion pairs with DNA. By x-ray crystallography, we compared the structures of the complexes with and without dithioation of the phosphate. Our NMR and x-ray data show that the lysine side chain in contact with the DNA phosphate becomes more dynamic upon dithioation. Our thermodynamic, structural, and dynamic investigations collectively suggest that the affinity enhancement by the oxygen-to-sulfur substitution in DNA phosphate is largely due to an entropic gain arising from mobilization of the intermolecular ion pair at the protein-DNA interface.
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Affiliation(s)
- Levani Zandarashvili
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas
| | - Dan Nguyen
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas
| | - Kurtis M Anderson
- Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, Texas
| | - Mark A White
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas
| | - David G Gorenstein
- Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, Texas
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas.
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Atreya HS, Sathyamoorthy B, Jaipuria G, Beaumont V, Varani G, Szyperski T. GFT projection NMR for efficient (1)H/ (13)C sugar spin system identification in nucleic acids. JOURNAL OF BIOMOLECULAR NMR 2012. [PMID: 23192291 DOI: 10.1007/s10858-012-9687-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A newly implemented G-matrix Fourier transform (GFT) (4,3)D HC(C)CH experiment is presented in conjunction with (4,3)D HCCH to efficiently identify (1)H/(13)C sugar spin systems in (13)C labeled nucleic acids. This experiment enables rapid collection of highly resolved relay 4D HC(C)CH spectral information, that is, shift correlations of (13)C-(1)H groups separated by two carbon bonds. For RNA, (4,3)D HC(C)CH takes advantage of the comparably favorable 1'- and 3'-CH signal dispersion for complete spin system identification including 5'-CH. The (4,3)D HC(C)CH/HCCH based strategy is exemplified for the 30-nucleotide 3'-untranslated region of the pre-mRNA of human U1A protein.
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Chaney BA, Clark-Baldwin K, Dave V, Ma J, Rance M. Solution structure of the K50 class homeodomain PITX2 bound to DNA and implications for mutations that cause Rieger syndrome. Biochemistry 2005; 44:7497-511. [PMID: 15895993 DOI: 10.1021/bi0473253] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have determined the solution structure of a complex containing the K50 class homeodomain Pituitary homeobox protein 2 (PITX2) bound to its consensus DNA site (TAATCC). Previous studies have suggested that residue 50 is an important determinant of differential DNA-binding specificity among homeodomains. Although structures of several homeodomain-DNA complexes have been determined, this is the first structure of a native K50 class homeodomain. The only K50 homeodomain structure determined previously is an X-ray crystal structure of an altered specificity mutant, Engrailed Q50K (EnQ50K). Analysis of the NMR structure of the PITX2 homeodomain indicates that the lysine at position 50 makes contacts with two guanines on the antisense strand of the DNA, adjacent to the TAAT core DNA sequence, consistent with the structure of EnQ50K. Our evidence suggests that this side chain may make fluctuating interactions with the DNA, which is complementary to the crystal data for EnQ50K. There are differences in the tertiary structure between the native K50 structure and that of EnQ50K, which may explain differences in affinity and specificity between these proteins. Mutations in the human PITX2 gene are responsible for Rieger syndrome, an autosomal dominant disorder. Analysis of the residues mutated in Rieger syndrome indicates that many of these residues are involved in DNA binding, while others are involved in formation of the hydrophobic core of the protein. Overall, the role of K50 in homeodomain recognition is further clarified, and the results indicate that native K50 homeodomains may exhibit differences from altered specificity mutants.
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Affiliation(s)
- Beth A Chaney
- Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, 231 Albert Sabin Way, Medical Sciences Building, Cincinnati, Ohio 45267-0524, USA
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Gutmanas A, Billeter M. Specific DNA recognition by theAntp homeodomain: MD simulations of specific and nonspecific complexes. Proteins 2004; 57:772-82. [PMID: 15468320 DOI: 10.1002/prot.20273] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Four molecular dynamics simulation trajectories of complexes between the wild-type or a mutant Antennapedia homeodomain and 2 DNA sequences were generated in order to probe the mechanisms governing the specificity of DNA recognition. The starting point was published affinity measurements showing that a single protein mutation combined with a replacement of 2 base pairs yields a new high-affinity complex, whereas the other combinations, with changes on only 1 macromolecule, exhibited lower affinity. The simulations of the 4 complexes yielded fluctuating networks of interaction. On average, these networks differ significantly, explaining the switch of affinity caused by the alterations in the macromolecules. The network of mostly hydrogen-bonding interactions involving several water molecules, which was suggested both by X-ray and NMR structures of the wild-type homeodomain and its DNA operator sequence, could be reproduced in the trajectory. More interestingly, the high-affinity complex with alterations in both the protein and the DNA yielded again a dynamic but very tight network of intermolecular interactions, however, attributing a significantly stronger role to direct hydrophobic interactions at the expense of water bridges. The other 2 homeodomain-DNA complexes, with only 1 molecule altered, show on average over the trajectories a clearly reduced number of protein-DNA interactions. The observations from these simulations suggest specific experiments and thus close the circle formed by biochemical, structural, and computational studies. The shift from a water-dominated to a more "dry" interface may prove important in the design of proteins binding DNA in a specific manner.
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Affiliation(s)
- Aleksandras Gutmanas
- Biophysics Group, Department of Chemistry, Göteborg University, Göteborg, Sweden
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Kojima C, Ono A, Ono A, Kainosho M. Solid-phase synthesis of selectively labeled DNA: applications for multidimensional nuclear magnetic resonance spectroscopy. Methods Enzymol 2002; 338:261-83. [PMID: 11460552 DOI: 10.1016/s0076-6879(02)38224-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The solid-phase chemical synthesis method has a strong advantage over the enzymatic method for preparing selectively labeled DNA oligomers. Atom-specific and fully labeled 2'-deoxynucleosides are economically prepared with routinely available isotope precursors using this synthetic route. Special DNA oligomers prepared by advanced labeling techniques are needed for advanced NMR applications, and chemical synthesis is the method of choice to respond to such demands. As a summary of this chapter, two tables are given. Table I lists the labeled nucleosides reported to be available by chemical syntheses. Table II lists the NMR studies using labeled DNA oligomers that were prepared by chemical syntheses.
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Affiliation(s)
- C Kojima
- Department of Chemistry, Japan Science and Technology Corporation & Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
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Iwahara J, Wojciak JM, Clubb RT. An efficient NMR experiment for analyzing sugar-puckering in unlabeled DNA: application to the 26-kDa dead ringer-DNA complex. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 153:262-266. [PMID: 11740904 DOI: 10.1006/jmre.2001.2448] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We present a new NMR experiment for estimating the type and degree of sugar-puckering in high-molecular-weight unlabeled DNA molecules. The experiment consists of a NOESY sequence preceded by a constant-time scalar coupling period. Two subexperiments are compared, each differing in the amount of time the (3)J(H3'H2') and (3)J(H3'H2") couplings are active on the H3' magnetization. The resultant data are easy to analyze, since a comparison of the signal intensities of any resolved NOE cross peak originating from H3' atoms of the duplex can be used to estimate the sum of the (3)J(H3'H2') and (3)J(H3'H2") couplings and thus the puckering type of the deoxyribose ring. Isotope filters to eliminate signals of the (13)C-labeled component in the F1-dimension are implemented, facilitating analyses of high-molecular-weight protein-DNA complexes containing (13)C-labeled protein and unlabeled DNA. The utility of the experiment is demonstrated on the 26-kDa Dead Ringer protein-DNA complex and reveals that the DNA uniformly adopts the S-type configuration when bound to protein.
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Affiliation(s)
- J Iwahara
- Department of Chemistry and Biochemistry, UCLA-DOE Laboratory of Structural Biology and Molecular Medicine, University of California, Los Angeles, 405 Hilgard Avenue, California 90095-1570, USA.
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