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Gupta R, Zhang H, Lu M, Hou G, Caporini M, Rosay M, Maas W, Struppe J, Ahn J, Byeon IJL, Oschkinat H, Jaudzems K, Barbet-Massin E, Emsley L, Pintacuda G, Lesage A, Gronenborn AM, Polenova T. Dynamic Nuclear Polarization Magic-Angle Spinning Nuclear Magnetic Resonance Combined with Molecular Dynamics Simulations Permits Detection of Order and Disorder in Viral Assemblies. J Phys Chem B 2019; 123:5048-5058. [PMID: 31125232 DOI: 10.1021/acs.jpcb.9b02293] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We report dynamic nuclear polarization (DNP)-enhanced magic-angle spinning (MAS) NMR spectroscopy in viral capsids from HIV-1 and bacteriophage AP205. Viruses regulate their life cycles and infectivity through modulation of their structures and dynamics. While static structures of capsids from several viruses are now accessible with near-atomic-level resolution, atomic-level understanding of functionally important motions in assembled capsids is lacking. We observed up to 64-fold signal enhancements by DNP, which permitted in-depth analysis of these assemblies. For the HIV-1 CA assemblies, a remarkably high spectral resolution in the 3D and 2D heteronuclear data sets permitted the assignment of a significant fraction of backbone and side-chain resonances. Using an integrated DNP MAS NMR and molecular dynamics (MD) simulation approach, the conformational space sampled by the assembled capsid at cryogenic temperatures was mapped. Qualitatively, a remarkable agreement was observed for the experimental 13C/15N chemical shift distributions and those calculated from substructures along the MD trajectory. Residues that are mobile at physiological temperatures are frozen out in multiple conformers at cryogenic conditions, resulting in broad experimental and calculated chemical shift distributions. Overall, our results suggest that DNP MAS NMR measurements in combination with MD simulations facilitate a thorough understanding of the dynamic signatures of viral capsids.
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Affiliation(s)
- Rupal Gupta
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Huilan Zhang
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Manman Lu
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Guangjin Hou
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Marc Caporini
- Bruker Biospin Corporation , 15 Fortune Drive , Billerica , Massachusetts 01821 , United States
| | - Melanie Rosay
- Bruker Biospin Corporation , 15 Fortune Drive , Billerica , Massachusetts 01821 , United States
| | - Werner Maas
- Bruker Biospin Corporation , 15 Fortune Drive , Billerica , Massachusetts 01821 , United States
| | - Jochem Struppe
- Bruker Biospin Corporation , 15 Fortune Drive , Billerica , Massachusetts 01821 , United States
| | | | | | - Hartmut Oschkinat
- Leibniz-Institut für Molekulare Pharmakologie , Robert-Roessle-Str. 10 , 13125 Berlin , Germany
| | - Kristaps Jaudzems
- Centre de RMN à Très Hauts Champs , Institut des Sciences Analytiques, UMR 5280 CNRS / Ecole Normale Supérieure de Lyon , 5 Rue de la Doua , Villeurbanne, 69100 Lyon , France
| | - Emeline Barbet-Massin
- Centre de RMN à Très Hauts Champs , Institut des Sciences Analytiques, UMR 5280 CNRS / Ecole Normale Supérieure de Lyon , 5 Rue de la Doua , Villeurbanne, 69100 Lyon , France
| | - Lyndon Emsley
- Institut des Sciences et Ingénierie Chimques , Ecole Polytechnique Fédérale de Lausanne (EPFL) CH-1015 Lausanne , Switzerland
| | - Guido Pintacuda
- Centre de RMN à Très Hauts Champs , Institut des Sciences Analytiques, UMR 5280 CNRS / Ecole Normale Supérieure de Lyon , 5 Rue de la Doua , Villeurbanne, 69100 Lyon , France
| | - Anne Lesage
- Centre de RMN à Très Hauts Champs , Institut des Sciences Analytiques, UMR 5280 CNRS / Ecole Normale Supérieure de Lyon , 5 Rue de la Doua , Villeurbanne, 69100 Lyon , France
| | | | - Tatyana Polenova
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
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Ebselen, a Small-Molecule Capsid Inhibitor of HIV-1 Replication. Antimicrob Agents Chemother 2016; 60:2195-208. [PMID: 26810656 DOI: 10.1128/aac.02574-15] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 01/20/2016] [Indexed: 12/21/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) capsid plays crucial roles in HIV-1 replication and thus represents an excellent drug target. We developed a high-throughput screening method based on a time-resolved fluorescence resonance energy transfer (HTS-TR-FRET) assay, using the C-terminal domain (CTD) of HIV-1 capsid to identify inhibitors of capsid dimerization. This assay was used to screen a library of pharmacologically active compounds, composed of 1,280in vivo-active drugs, and identified ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], an organoselenium compound, as an inhibitor of HIV-1 capsid CTD dimerization. Nuclear magnetic resonance (NMR) spectroscopic analysis confirmed the direct interaction of ebselen with the HIV-1 capsid CTD and dimer dissociation when ebselen is in 2-fold molar excess. Electrospray ionization mass spectrometry revealed that ebselen covalently binds the HIV-1 capsid CTD, likely via a selenylsulfide linkage with Cys198 and Cys218. This compound presents anti-HIV activity in single and multiple rounds of infection in permissive cell lines as well as in primary peripheral blood mononuclear cells. Ebselen inhibits early viral postentry events of the HIV-1 life cycle by impairing the incoming capsid uncoating process. This compound also blocks infection of other retroviruses, such as Moloney murine leukemia virus and simian immunodeficiency virus, but displays no inhibitory activity against hepatitis C and influenza viruses. This study reports the use of TR-FRET screening to successfully identify a novel capsid inhibitor, ebselen, validating HIV-1 capsid as a promising target for drug development.
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Gupta R, Lu M, Hou G, Caporini MA, Rosay M, Maas W, Struppe J, Suiter C, Ahn J, Byeon IJL, Franks WT, Orwick-Rydmark M, Bertarello A, Oschkinat H, Lesage A, Pintacuda G, Gronenborn AM, Polenova T. Dynamic Nuclear Polarization Enhanced MAS NMR Spectroscopy for Structural Analysis of HIV-1 Protein Assemblies. J Phys Chem B 2016; 120:329-39. [PMID: 26709853 DOI: 10.1021/acs.jpcb.5b12134] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mature infectious HIV-1 virions contain conical capsids composed of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20-64-fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar-based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4-18.8 T) and temperature (109-180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of the temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine side-chain conformers; unique intermolecular correlations across two CA molecules; and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR spectroscopy as an excellent tool for the characterization of HIV-1 assemblies.
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Affiliation(s)
- Rupal Gupta
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
| | - Manman Lu
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
| | - Guangjin Hou
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
| | - Marc A Caporini
- Bruker Biospin Corporation , 15 Fortune Drive, Billerica, Massachusetts United States
| | - Melanie Rosay
- Bruker Biospin Corporation , 15 Fortune Drive, Billerica, Massachusetts United States
| | - Werner Maas
- Bruker Biospin Corporation , 15 Fortune Drive, Billerica, Massachusetts United States
| | - Jochem Struppe
- Bruker Biospin Corporation , 15 Fortune Drive, Billerica, Massachusetts United States
| | - Christopher Suiter
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
| | | | | | - W Trent Franks
- Leibniz-Institut für Molekulare Pharmakologie , Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Marcella Orwick-Rydmark
- Leibniz-Institut für Molekulare Pharmakologie , Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Andrea Bertarello
- Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques, UMR 5280 CNRS/Ecole Normale Supérieure de Lyon , 5 rue de la Doua, 69100 Villeurbanne (Lyon), France
| | - Hartmut Oschkinat
- Leibniz-Institut für Molekulare Pharmakologie , Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Anne Lesage
- Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques, UMR 5280 CNRS/Ecole Normale Supérieure de Lyon , 5 rue de la Doua, 69100 Villeurbanne (Lyon), France
| | - Guido Pintacuda
- Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques, UMR 5280 CNRS/Ecole Normale Supérieure de Lyon , 5 rue de la Doua, 69100 Villeurbanne (Lyon), France
| | | | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
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Han Y, Hou G, Suiter CL, Ahn J, Byeon IJL, Lipton AS, Burton S, Hung I, Gor'kov PL, Gan Z, Brey W, Rice D, Gronenborn AM, Polenova T. Magic angle spinning NMR reveals sequence-dependent structural plasticity, dynamics, and the spacer peptide 1 conformation in HIV-1 capsid protein assemblies. J Am Chem Soc 2013; 135:17793-803. [PMID: 24164646 DOI: 10.1021/ja406907h] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A key stage in HIV-1 maturation toward an infectious virion requires sequential proteolytic cleavage of the Gag polyprotein leading to the formation of a conical capsid core that encloses the viral RNA genome and a small complement of proteins. The final step of this process involves severing the SP1 peptide from the CA-SP1 maturation intermediate, which triggers the condensation of the CA protein into the capsid shell. The details of the overall mechanism, including the conformation of the SP1 peptide in CA-SP1, are still under intense debate. In this report, we examine tubular assemblies of CA and the CA-SP1 maturation intermediate using magic angle spinning (MAS) NMR spectroscopy. At magnetic fields of 19.9 T and above, outstanding quality 2D and 3D MAS NMR spectra were obtained for tubular CA and CA-SP1 assemblies, permitting resonance assignments for subsequent detailed structural characterization. Dipolar- and scalar-based correlation experiments unequivocally indicate that SP1 peptide is in a random coil conformation and mobile in the assembled CA-SP1. Analysis of two CA protein sequence variants reveals that, unexpectedly, the conformations of the SP1 tail, the functionally important CypA loop, and the loop preceding helix 8 are modulated by residue variations at distal sites. These findings provide support for the role of SP1 as a trigger of the disassembly of the immature CA capsid for its subsequent de novo reassembly into mature cores and establish the importance of sequence-dependent conformational plasticity in CA assembly.
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Affiliation(s)
- Yun Han
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
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Byeon IJL, Hou G, Han Y, Suiter CL, Ahn J, Jung J, Byeon CH, Gronenborn AM, Polenova T. Motions on the millisecond time scale and multiple conformations of HIV-1 capsid protein: implications for structural polymorphism of CA assemblies. J Am Chem Soc 2012; 134:6455-66. [PMID: 22428579 PMCID: PMC3325613 DOI: 10.1021/ja300937v] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The capsid protein (CA) of human immunodeficiency virus 1 (HIV-1) assembles into a cone-like structure that encloses the viral RNA genome. Interestingly, significant heterogeneity in shape and organization of capsids can be observed in mature HIV-1 virions. In vitro, CA also exhibits structural polymorphism and can assemble into various morphologies, such as cones, tubes, and spheres. Many intermolecular contacts that are critical for CA assembly are formed by its C-terminal domain (CTD), a dimerization domain, which was found to adopt different orientations in several X-ray and NMR structures of the CTD dimer and full-length CA proteins. Tyr145 (Y145), residue two in our CTD construct used for NMR structure determination, but not present in the crystallographic constructs, was found to be crucial for infectivity and engaged in numerous interactions at the CTD dimer interface. Here we investigate the origin of CA structural plasticity using solid-state NMR and solution NMR spectroscopy. In the solid state, the hinge region connecting the NTD and CTD is flexible on the millisecond time scale, as evidenced by the backbone motions of Y145 in CA conical assemblies and in two CTD constructs (137-231 and 142-231), allowing the protein to access multiple conformations essential for pleimorphic capsid assemblies. In solution, the CTD dimer exists as two major conformers, whose relative populations differ for the different CTD constructs. In the longer CTD (144-231) construct that contains the hinge region between the NTD and CTD, the populations of the two conformers are likely determined by the protonation state of the E175 side chain that is located at the dimer interface and within hydrogen-bonding distance of the W184 side chain on the other monomer. At pH 6.5, the major conformer exhibits the same dimer interface as full-length CA. In the short CTD (150-231) construct, no pH-dependent conformational shift is observed. These findings suggest that the presence of structural plasticity at the CTD dimer interface permits pleiotropic HIV-1 capsid assembly, resulting in varied capsid morphologies.
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Affiliation(s)
- In-Ja L. Byeon
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Guangjin Hou
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Yun Han
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Christopher L. Suiter
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Jinwoo Ahn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Jinwon Jung
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Chang-Hyeock Byeon
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Angela M. Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Tatyana Polenova
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
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Hou G, Byeon IJL, Ahn J, Gronenborn AM, Polenova T. 1H-13C/1H-15N heteronuclear dipolar recoupling by R-symmetry sequences under fast magic angle spinning for dynamics analysis of biological and organic solids. J Am Chem Soc 2011; 133:18646-55. [PMID: 21995349 DOI: 10.1021/ja203771a] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fast magic angle spinning (MAS) NMR spectroscopy is becoming increasingly important in structural and dynamics studies of biological systems and inorganic materials. Superior spectral resolution due to the efficient averaging of the dipolar couplings can be attained at MAS frequencies of 40 kHz and higher with appropriate decoupling techniques, while proton detection gives rise to significant sensitivity gains, therefore making fast MAS conditions advantageous across the board compared with the conventional slow- and moderate-MAS approaches. At the same time, many of the dipolar recoupling approaches that currently constitute the basis for structural and dynamics studies of solid materials and that are designed for MAS frequencies of 20 kHz and below, fail above 30 kHz. In this report, we present an approach for (1)H-(13)C/(1)H-(15)N heteronuclear dipolar recoupling under fast MAS conditions using R-type symmetry sequences, which is suitable even for fully protonated systems. A series of rotor-synchronized R-type symmetry pulse schemes are explored for the determination of structure and dynamics in biological and organic systems. The investigations of the performance of the various RN(n)(v)-symmetry sequences at the MAS frequency of 40 kHz experimentally and by numerical simulations on [U-(13)C,(15)N]-alanine and [U-(13)C,(15)N]-N-acetyl-valine, revealed excellent performance for sequences with high symmetry number ratio (N/2n > 2.5). Further applications of this approach are presented for two proteins, sparsely (13)C/uniformly (15)N-enriched CAP-Gly domain of dynactin and U-(13)C,(15)N-Tyr enriched C-terminal domain of HIV-1 CA protein. Two-dimensional (2D) and 3D R16(3)(2)-based DIPSHIFT experiments carried out at the MAS frequency of 40 kHz, yielded site-specific (1)H-(13)C/(1)H-(15)N heteronuclear dipolar coupling constants for CAP-Gly and CTD CA, reporting on the dynamic behavior of these proteins on time scales of nano- to microseconds. The R-symmetry-based dipolar recoupling under fast MAS is expected to find numerous applications in studies of protein assemblies and organic solids by MAS NMR spectroscopy.
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Affiliation(s)
- Guangjin Hou
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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Han Y, Ahn J, Concel J, Byeon IJL, Gronenborn AM, Yang J, Polenova T. Solid-state NMR studies of HIV-1 capsid protein assemblies. J Am Chem Soc 2010; 132:1976-87. [PMID: 20092249 PMCID: PMC2829833 DOI: 10.1021/ja908687k] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In mature HIV-1 virions, the 26.6 kDa CA protein is assembled into a characteristic cone-shaped core (capsid) that encloses the RNA viral genome. The assembled capsid structure is best described by a fullerene cone model that is made up from a hexameric lattice containing a variable number of CA pentamers, thus allowing for closure of tubular or conical structures. In this paper, we present a solid-state NMR analysis of the wild-type HIV-1 CA protein, prepared as conical and spherical assemblies that are stable and are not affected by magic angle spinning of the samples at frequencies between 10 and 25 kHz. Multidimensional homo- and heteronuclear correlation spectra of CA assemblies of uniformly (13)C,(15)N-labeled CA exhibit narrow lines, indicative of the conformational homogeneity of the protein in these assemblies. For the conical assemblies, partial residue-specific resonance assignments were obtained. Analysis of the NMR spectra recorded for the conical and spherical assemblies indicates that the CA protein structure is not significantly different in the different morphologies. The present results demonstrate that the assemblies of CA protein are amenable to detailed structural analysis by solid-state NMR spectroscopy.
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Affiliation(s)
- Yun Han
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Jinwoo Ahn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Jason Concel
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - In-Ja L. Byeon
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Angela M. Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Jun Yang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Tatyana Polenova
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
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