1
|
Cai M, Agarwal N, Garrett DS, Baber J, Clore GM. A Transient, Excited Species of the Autoinhibited α-State of the Bacterial Transcription Factor RfaH May Represent an Early Intermediate on the Fold-Switching Pathway. Biochemistry 2024; 63:2030-2039. [PMID: 39088556 DOI: 10.1021/acs.biochem.4c00258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2024]
Abstract
RfaH is a two-domain transcription factor in which the C-terminal domain switches fold from an α-helical hairpin to a β-roll upon binding the ops-paused RNA polymerase. To ascertain the presence of a sparsely populated excited state that may prime the autoinhibited resting state of RfaH for binding ops-paused RNA polymerase, we carried out a series of NMR-based exchange experiments to probe for conformational exchange on the millisecond time scale. Quantitative analysis of these data reveals exchange between major ground (∼95%) and sparsely populated excited (∼5%) states with an exchange lifetime of ∼3 ms involving residues at the interface between the N-terminal and C-terminal domains formed by the β3/β4 hairpin and helix α3 of the N-terminal domain and helices α4 and α5 of the C-terminal domain. The largest 15N backbone chemical shift differences are associated with the β3/β4 hairpin, leading us to suggest that the excited state may involve a rigid body lateral displacement/rotation away from the C-terminal domain to adopt a position similar to that seen in the active RNA polymerase-bound state. Such a rigid body reorientation would result in a reduction in the interface between the N- and C-terminal domains with the possible introduction of a cavity or cavities. This hypothesis is supported by the observation that the population of the excited species and the exchange rate of interconversion between ground and excited states are reduced at a high (2.5 kbar) pressure. Mechanistic implications for fold switching of the C-terminal domain in the context of RNA polymerase binding are discussed.
Collapse
Affiliation(s)
- Mengli Cai
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Nipanshu Agarwal
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Daniel S Garrett
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - James Baber
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - G Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| |
Collapse
|
2
|
He L, McAndrew R, Barbu R, Gifford G, Halacoglu C, Drouin-Allaire C, Weber L, Kristensen LG, Gupta S, Chen Y, Petzold CJ, Allaire M, Li KH, Ralston CY, Gochin M. Structure and Interactions of HIV-1 gp41 CHR-NHR Reverse Hairpin Constructs Reveal Molecular Determinants of Antiviral Activity. J Mol Biol 2024; 436:168650. [PMID: 38866091 PMCID: PMC11297672 DOI: 10.1016/j.jmb.2024.168650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Revised: 06/05/2024] [Accepted: 06/05/2024] [Indexed: 06/14/2024]
Abstract
Engineered reverse hairpin constructs containing a partial C-heptad repeat (CHR) sequence followed by a short loop and full-length N-heptad repeat (NHR) were previously shown to form trimers in solution and to be nanomolar inhibitors of HIV-1 Env mediated fusion. Their target is the in situ gp41 fusion intermediate, and they have similar potency to other previously reported NHR trimers. However, their design implies that the NHR is partially covered by CHR, which would be expected to limit potency. An exposed hydrophobic pocket in the folded structure may be sufficient to confer the observed potency, or they may exist in a partially unfolded state exposing full length NHR. Here we examined their structure by crystallography, CD and fluorescence, establishing that the proteins are folded hairpins both in crystal form and in solution. We examined unfolding in the milieu of the fusion reaction by conducting experiments in the presence of a membrane mimetic solvent and by engineering a disulfide bond into the structure to prevent partial unfolding. We further examined the role of the hydrophobic pocket, using a hairpin-small molecule adduct that occluded the pocket, as confirmed by X-ray footprinting. The results demonstrated that the NHR region nominally covered by CHR in the engineered constructs and the hydrophobic pocket region that is exposed by design were both essential for nanomolar potency and that interaction with membrane is likely to play a role in promoting the required inhibitor structure. The design concepts can be applied to other Class 1 viral fusion proteins.
Collapse
Affiliation(s)
- Li He
- Department of Foundational Biomedical Sciences, Touro University California College of Osteopathic Medicine, 1310 Club Drive, Mare Island, Vallejo, CA 94592, USA
| | - Ryan McAndrew
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Razvan Barbu
- Master of Science in Medical Health Sciences, Touro University California College of Osteopathic Medicine, 1310 Club Drive, Mare Island, Vallejo, CA 94592, USA
| | - Grant Gifford
- Master of Science in Medical Health Sciences, Touro University California College of Osteopathic Medicine, 1310 Club Drive, Mare Island, Vallejo, CA 94592, USA
| | - Cari Halacoglu
- Master of Science in Medical Health Sciences, Touro University California College of Osteopathic Medicine, 1310 Club Drive, Mare Island, Vallejo, CA 94592, USA
| | - Camille Drouin-Allaire
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Lindsey Weber
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Line G Kristensen
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Sayan Gupta
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Yan Chen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Christopher J Petzold
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Marc Allaire
- Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Kathy H Li
- Department of Pharmaceutical Chemistry, UCSF School of Pharmacy, San Francisco, CA 94143, USA
| | - Corie Y Ralston
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Miriam Gochin
- Department of Foundational Biomedical Sciences, Touro University California College of Osteopathic Medicine, 1310 Club Drive, Mare Island, Vallejo, CA 94592, USA; Department of Pharmaceutical Chemistry, UCSF School of Pharmacy, San Francisco, CA 94143, USA.
| |
Collapse
|
3
|
Santoro A, Buonocore M, Firoznezhad M, Grimaldi M, D'Ursi AM. Conformational analysis of a new peptide derived from feline immunodeficiency virus gp36 in SDS micelles: An NMR-MD based investigation. J Pept Sci 2024:e3645. [PMID: 39030892 DOI: 10.1002/psc.3645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 06/27/2024] [Accepted: 06/28/2024] [Indexed: 07/22/2024]
Abstract
Feline immunodeficiency virus (FIV) shares structural similarities with human immunodeficiency virus (HIV): the surface glycoprotein gp36 corresponds to the HIV gp41, which drives virus-host cell interactions and is targeted by the peptide entry inhibitor enfuvirtide. Following a similar drug design strategy for the development of an anti-FIV therapy, the present study investigates 627-646gp36 NHR, a peptide sequence derived from a region of gp36 that was previously found to interfere with the antiviral activity of the peptide C8, which instead derives from the gp36 MPER. CD, NMR, and MD simulations were employed to probe the conformational characteristics of 627-646gp36 NHR in the membrane-mimicking environment of SDS micelles. Our data show that 627-646gp36 NHR is characterized by three dynamic helix structures. MD simulations involving 627-646gp36 NHR, C8, and a larger protein, including the CHR and MPER regions, suggest that the interaction of C8 with the MPER region, the origin of the antiviral activity of C8, is disfavored in the presence of 627-646gp36 NHR in the simulation. This evidence can be useful for interpreting the molecular mechanism that leads to interference with the activity of C8, providing information on the folding/unfolding mechanism of the viral glycoprotein to design new strategies to inhibit viral entry.
Collapse
Affiliation(s)
- Angelo Santoro
- Department of Pharmacy, University of Salerno, Fisciano, Italy
- Department of Pharmacy, Scuola di Specializzazione in Farmacia Ospedaliera, University of Salerno, Italy
| | - Michela Buonocore
- Department of Chemical Sciences and Research Centre on Bioactive Peptides (CIRPeB), University of Naples Federico II, Naples, Italy
| | - Mohammad Firoznezhad
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Trento, Italy
| | | | | |
Collapse
|
4
|
Shiraishi Y, Shimada I. NMR Characterization of the Papain-like Protease from SARS-CoV-2 Identifies the Conformational Heterogeneity in Its Inhibitor-Binding Site. J Am Chem Soc 2023. [PMID: 37478405 DOI: 10.1021/jacs.3c04115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Papain-like protease (PLpro) from severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is a prime target for the development of antivirals for Coronavirus disease 2019 (COVID-19). However, drugs that target the PLpro protein have not yet been approved. In order to gain insights into the development of a PLpro inhibitor, conformational dynamics of PLpro in complex with GRL0617, the most well-characterized PLpro inhibitor, were investigated using nuclear magnetic resonance (NMR) spectroscopy in solution. Although mutational analyses demonstrated that the L162 sidechain interaction is responsible for the affinity for GRL0617, NMR analyses revealed that L162 in the inhibitor-binding pocket underwent conformational exchange and was not fixed in the conformation in which it formed a contact with ortho-methyl group of GRL0617. The identified conformational dynamics would provide a rationale for the binding mechanism of a covalent inhibitor designed based on GRL0617.
Collapse
Affiliation(s)
- Yutaro Shiraishi
- Laboratory for Dynamic Structure of Biomolecules, RIKEN Center for Biosystems Dynamics Research (BDR), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Ichio Shimada
- Laboratory for Dynamic Structure of Biomolecules, RIKEN Center for Biosystems Dynamics Research (BDR), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
- Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4, Kagamiyama, Higashi-Hiroshima 739-8528, Japan
| |
Collapse
|
5
|
Rokonujjaman M, Sahyouni A, Wolfe R, Jia L, Ghosh U, Weliky DP. A large HIV gp41 construct with trimer-of-hairpins structure exhibits V2E mutation-dominant attenuation of vesicle fusion and helicity very similar to V2E attenuation of HIV fusion and infection and supports: (1) hairpin stabilization of membrane apposition with larger distance for V2E; and (2) V2E dominance by an antiparallel β sheet with interleaved fusion peptide strands from two gp41 trimers. Biophys Chem 2023; 293:106933. [PMID: 36508984 PMCID: PMC9879285 DOI: 10.1016/j.bpc.2022.106933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 11/27/2022]
Abstract
There is complete attenuation of fusion and infection mediated by HIV gp160 with gp41 subunit with V2E mutation, and also V2E dominance with WT/V2E mixtures. V2E is at the N-terminus of the ∼25-residue fusion peptide (Fp) which likely binds the target membrane. In this study, large V2E attenuation and dominance were observed for vesicle fusion induced by FP_HM, a large gp41 ectodomain construct with Fp followed by hyperthermostable hairpin with N- and C-helices, and membrane-proximal external region (Mper). FP_HM is a trimer-of-hairpins, the final gp41 structure during fusion. Vesicle fusion and helicity were measured for FP_HM using trimers with different fractions (f's) of WT and V2E proteins. Reductions in FP_HM fusion and helicity vs. fV2E were quantitatively-similar to those for gp160-mediated fusion and infection. Global fitting of all V2E data supports 6 WT gp41 (2 trimers) required for fusion. These data are understood by a model in which the ∼25 kcal/mol free energy for initial membrane apposition is compensated by the thermostable hairpin between the Fp in target membrane and Mper/transmembrane domain in virus membrane. The data support a structural model for V2E dominance with a membrane-bound Fp with antiparallel β sheet and interleaved strands from the two trimers. Relative to fV2E = 0, a longer Fp sheet is stabilized with small fV2E because of salt-bridge and/or hydrogen bonds between E2 on one strand and C-terminal Fp residues on adjacent strands, like R22. A longer Fp sheet results in shorter N- and C-helices, and larger separation during membrane apposition which hinders fusion.
Collapse
Affiliation(s)
- Md Rokonujjaman
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Abdulrazak Sahyouni
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Robert Wolfe
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Lihui Jia
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Ujjayini Ghosh
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
| |
Collapse
|
6
|
Wernersson S, Bobby R, Flavell L, Milbradt AG, Holdgate GA, Embrey KJ, Akke M. Bromodomain Interactions with Acetylated Histone 4 Peptides in the BRD4 Tandem Domain: Effects on Domain Dynamics and Internal Flexibility. Biochemistry 2022; 61:2303-2318. [PMID: 36215732 PMCID: PMC9631989 DOI: 10.1021/acs.biochem.2c00226] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The bromodomain and extra-terminal (BET) protein BRD4
regulates
gene expression via recruitment of transcriptional regulatory complexes
to acetylated chromatin. Like other BET proteins, BRD4 contains two
bromodomains, BD1 and BD2, that can interact cooperatively with target
proteins and designed ligands, with important implications for drug
discovery. Here, we used nuclear magnetic resonance (NMR) spectroscopy
to study the dynamics and interactions of the isolated bromodomains,
as well as the tandem construct including both domains and the intervening
linker, and investigated the effects of binding a tetra-acetylated
peptide corresponding to the tail of histone 4. The peptide affinity
is lower for both domains in the tandem construct than for the isolated
domains. Using 15N spin relaxation, we determined the global
rotational correlation times and residue-specific order parameters
for BD1 and BD2. Isolated BD1 is monomeric in the apo state but apparently
dimerizes upon binding the tetra-acetylated peptide. Isolated BD2
partially dimerizes in both the apo and peptide-bound states. The
backbone order parameters reveal marked differences between BD1 and
BD2, primarily in the acetyl-lysine binding site where the ZA loop
is more flexible in BD2. Peptide binding reduces the order parameters
of the ZA loop in BD1 and the ZA and BC loops in BD2. The AB loop,
located distally from the binding site, shows variable dynamics that
reflect the different dimerization propensities of the domains. These
results provide a basis for understanding target recognition by BRD4.
Collapse
Affiliation(s)
- Sven Wernersson
- Biophysical Chemistry, Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00Lund, Sweden
| | - Romel Bobby
- Mechanistic and Structural Biology, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, CambridgeCB4 0WG, U.K
| | - Liz Flavell
- Discovery Biology, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Cambridge Science Park, CambridgeCB4 0WG, U.K
| | - Alexander G Milbradt
- Mechanistic and Structural Biology, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, CambridgeCB4 0WG, U.K
| | - Geoffrey A Holdgate
- Mechanistic and Structural Biology, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, CambridgeCB4 0WG, U.K
| | - Kevin J Embrey
- Mechanistic and Structural Biology, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, CambridgeCB4 0WG, U.K
| | - Mikael Akke
- Biophysical Chemistry, Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00Lund, Sweden
| |
Collapse
|
7
|
Taiwo KM, Nam H, LeBlanc RM, Longhini AP, Dayie TK. Cross-correlated relaxation rates provide facile exchange signature in selectively labeled RNA. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 342:107245. [PMID: 35908529 DOI: 10.1016/j.jmr.2022.107245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 05/21/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Gerhard Wagner has made numerous contributions to NMR spectroscopy, particularly his developments in the field of spin-relaxation stand out in directly mapping the spectral density functions of proteins. He and his group developed experimental techniques to reveal the importance of dynamics to protein biological function and drug discovery. On his 75th birthday, we take this opportunity to highlight how some of those seminal ideas developed for proteins are being extended to RNAs. The role of dynamics in the structure and function of RNA has been a major interest in drug design and therapeutics. Here we present the use of cross-correlated relaxation rates (ηxy) from anti-TROSY (R2α) and TROSY (R2β) to rapidly obtain qualitative information about the chemical exchange taking place within the bacterial and human A-site RNA system while reducing the sets of relaxation experiments required to map dynamics. We show that ηxy correlates with the order parameter which gives information on how flexible or rigid a residue is. We further show R2β/ηxy can rapidly be used to probe chemical exchange as seen from its agreement with Rex. In addition, we report the ability of R2β/ηxy to determine chemical exchange taking place within the bacterial A-site RNA during structural transitions at pH 6.2 and 6.5. Finally, comparison of the R2β/ηxy ratios indicates bacterial A-site has greater R2β/ηxy values for G19 (1.34 s-1), A20 (1.38 s-1), U23 (1.63 s-1) and C24 (1.51 s-1) than human A-site [A19 (0.76 s-1), A20 (1.01 s-1), U23 (0.74 s-1) and C24 (0.71 s-1)]. Taken together, we have shown that the chemical exchange can quickly be analyzed for RNA systems from cross-correlated relaxation rates.
Collapse
Affiliation(s)
- Kehinde M Taiwo
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States.
| | - Hyeyeon Nam
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States
| | - Regan M LeBlanc
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States
| | - Andrew P Longhini
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States
| | - Theodore K Dayie
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, United States.
| |
Collapse
|
8
|
Olenginski LT, Kasprzak WK, Bergonzo C, Shapiro BA, Dayie TK. Conformational Dynamics of the Hepatitis B Virus Pre-genomic RNA on Multiple Time Scales: Implications for Viral Replication. J Mol Biol 2022; 434:167633. [PMID: 35595167 DOI: 10.1016/j.jmb.2022.167633] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/28/2022] [Accepted: 05/07/2022] [Indexed: 12/30/2022]
Abstract
Human hepatitis B virus (HBV) replication is initiated by the binding of the viral polymerase (P) to epsilon (ε), an ≈85-nucleotide (nt) cis-acting regulatory stem-loop RNA located at the 5'-end of the pre-genomic RNA (pgRNA). This interaction triggers P and pgRNA packaging and protein-primed reverse transcription and is therefore an attractive therapeutic target. Our recent nuclear magnetic resonance (NMR) structure of ε provides a useful starting point toward a detailed understanding of HBV replication, and hints at the functional importance of ε dynamics. Here, we present a detailed description of ε motions on the ps to ns and μs to ms time scales by NMR spin relaxation and relaxation dispersion, respectively. We also carried out molecular dynamics simulations to provide additional insight into ε conformational dynamics. These data outline a series of complex motions on multiple time scales within ε. Moreover, these motions occur in mostly conserved nucleotides from structural regions (i.e., priming loop, pseudo-triloop, and U43 bulge) that biochemical and mutational studies have shown to be essential for P binding, P-pgRNA packaging, protein-priming, and DNA synthesis. Taken together, our work implicates RNA dynamics as an integral feature that governs HBV replication.
Collapse
Affiliation(s)
- Lukasz T Olenginski
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Wojciech K Kasprzak
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Christina Bergonzo
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and University of Maryland, Rockville, MD 20850, USA
| | - Bruce A Shapiro
- RNA Biology Laboratory, National Cancer Institute, Frederick, MD 21702, USA
| | - Theodore K Dayie
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
| |
Collapse
|
9
|
Salnikov E, Aisenbrey C, Bechinger B. Lipid saturation and head group composition have a pronounced influence on the membrane insertion equilibrium of amphipathic helical polypeptides. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183844. [PMID: 34954200 DOI: 10.1016/j.bbamem.2021.183844] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/09/2021] [Accepted: 12/13/2021] [Indexed: 10/19/2022]
Abstract
The histidine-rich peptides of the LAH4 family were designed using cationic antimicrobial peptides such as magainin and PGLa as templates. The LAH4 amphipathic helical sequences exhibit a multitude of interesting biological properties such as antimicrobial activity, cell penetration of a large variety of cargo and lentiviral transduction enhancement. The parent peptide associates with lipid bilayers where it changes from an orientation along the membrane interface into a transmembrane configuration in a pH-dependent manner. Here we show that LAH4 adopts a transmembrane configuration in fully saturated DMPC membranes already at pH 3.5, i.e. much below the pKa of the histidines whereas the transition pH in POPC correlates closely with histidine neutralization. In contrast in POPG membranes the in-planar configuration is stabilized by about one pH unit. The differences in pH can be converted into energetic contributions for the in-plane to transmembrane transition equilibrium, where the shift in the transition pH due to lipid saturation corresponds to energies which are otherwise obtained by the exchange of several cationic with hydrophobic residues. A similar dependence on lipid saturation has also been observed when the PGLa and magainin antimicrobial peptides interact within lipid bilayers suggesting that the quantitative evaluation presented in this paper also applies to other membrane polypeptides.
Collapse
Affiliation(s)
- Evgeniy Salnikov
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France
| | - Christopher Aisenbrey
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France
| | - Burkhard Bechinger
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France; Institut Universitaire de France, France.
| |
Collapse
|
10
|
Ghosh U, Weliky DP. Rapid 2H NMR Transverse Relaxation of Perdeuterated Lipid Acyl Chains of Membrane with Bound Viral Fusion Peptide Supports Large-Amplitude Motions of These Chains That Can Catalyze Membrane Fusion. Biochemistry 2021; 60:2637-2651. [PMID: 34436856 DOI: 10.1021/acs.biochem.1c00316] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
An early step in cellular infection by a membrane-enveloped virus like HIV or influenza is joining (fusion) of the viral and cell membranes. Fusion is catalyzed by a viral protein that typically includes an apolar "fusion peptide" (fp) segment that binds the target membrane prior to fusion. In this study, the effects of nonhomologous HIV and influenza fp's on lipid acyl chain motion are probed with 2H NMR transverse relaxation rates (R2's) of a perdeuterated DMPC membrane. Measurements were made between 35 and 0 °C, which brackets the membrane liquid-crystalline-to-gel phase transitions. Samples were made with either HIV "GPfp" at pH 7 or influenza "HAfp" at pH 5 or 7. GPfp induces vesicle fusion at pH 7, and HAfp induces more fusion at pH 5 vs 7. GPfp bound to DMPC adopts an intermolecular antiparallel β sheet structure, whereas HAfp is a monomer helical hairpin. The R2's of the no peptide and HAfp, pH 7, samples increase gradually as temperature is lowered. The R2's of GPfp and HAfp, pH 5, samples have very different temperature dependence, with a ∼10× increase in R2CD2 when temperature is reduced from 25 to 20 °C and smaller but still substantial R2's at 10 and 0 °C. The large R2's with GPfp and HAfp, pH 5, are consistent with large-amplitude motions of lipid acyl chains that can aid fusion catalysis by increasing the population of chains near the aqueous phase, which is the chain location for transition states between membrane fusion intermediates.
Collapse
Affiliation(s)
- Ujjayini Ghosh
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| |
Collapse
|
11
|
LeBlanc RM, Kasprzak WK, Longhini AP, Olenginski LT, Abulwerdi F, Ginocchio S, Shields B, Nyman J, Svirydava M, Del Vecchio C, Ivanic J, Schneekloth JS, Shapiro BA, Dayie TK, Le Grice SFJ. Structural insights of the conserved "priming loop" of hepatitis B virus pre-genomic RNA. J Biomol Struct Dyn 2021; 40:9761-9773. [PMID: 34155954 PMCID: PMC10167916 DOI: 10.1080/07391102.2021.1934544] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/20/2021] [Indexed: 12/16/2022]
Abstract
Initiation of protein-primed (-) strand DNA synthesis in hepatitis B virus (HBV) requires interaction of the viral polymerase with a cis-acting regulatory signal, designated epsilon (ε), located at the 5'-end of its pre-genomic RNA (pgRNA). Binding of polymerase to ε is also necessary for pgRNA encapsidation. While the mechanistic basis of this interaction remains elusive, mutagenesis studies suggest its internal 6-nt "priming loop" provides an important structural contribution. ε might therefore be considered a promising target for small molecule interventions to complement current nucleoside-analog based anti-HBV therapies. An ideal prerequisite to any RNA-directed small molecule strategy would be a detailed structural description of this important element. Herein, we present a solution NMR structure for HBV ε which, in combination with molecular dynamics and docking simulations, reports on a flexible ligand "pocket", reminiscent of those observed in proteins. We also demonstrate the binding of the selective estrogen receptor modulators (SERMs) Raloxifene, Bazedoxifene, and a de novo derivative to the priming loop.Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Regan M. LeBlanc
- Basic Research Laboratory, National Cancer Institute, Frederick, MD, USA
- Vertex Pharmaceuticals, Boston, MA, USA
| | - Wojciech K. Kasprzak
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Andrew P. Longhini
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA
| | - Lukasz T. Olenginski
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | - Fardokht Abulwerdi
- Basic Research Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Stefano Ginocchio
- Basic Research Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Brigit Shields
- RNA Biology Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Julie Nyman
- Basic Research Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Maryia Svirydava
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | | | - Joseph Ivanic
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | | | - Bruce A. Shapiro
- RNA Biology Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Theodore Kwaku Dayie
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | | |
Collapse
|
12
|
Olenginski LT, Dayie TK. Quantifying the effects of long-range 13C- 13C dipolar coupling on measured relaxation rates in RNA. JOURNAL OF BIOMOLECULAR NMR 2021; 75:203-211. [PMID: 33914223 PMCID: PMC8131303 DOI: 10.1007/s10858-021-00368-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 04/05/2021] [Indexed: 06/12/2023]
Abstract
Selective stable isotope labeling has transformed structural and dynamics analysis of RNA by NMR spectroscopy. These methods can remove 13C-13C dipolar couplings that complicate 13C relaxation analyses. While these phenomena are well documented for sites with adjacent 13C nuclei (e.g. ribose C1'), less is known about so-called isolated sites (e.g. adenosine C2). To investigate and quantify the effects of long-range (> 2 Å) 13C-13C dipolar interactions on RNA dynamics, we simulated adenosine C2 relaxation rates in uniformly [U-13C/15N]-ATP or selectively [2-13C]-ATP labeled RNAs. Our simulations predict non-negligible 13C-13C dipolar contributions from adenosine C4, C5, and C6 to C2 longitudinal (R1) relaxation rates in [U-13C/15N]-ATP labeled RNAs. Moreover, these contributions increase at higher magnetic fields and molecular weights to introduce discrepancies that exceed 50%. This will become increasingly important at GHz fields. Experimental R1 measurements in the 61 nucleotide human hepatitis B virus encapsidation signal ε RNA labeled with [U-13C/15N]-ATP or [2-13C]-ATP corroborate these simulations. Thus, in the absence of selectively labeled samples, long-range 13C-13C dipolar contributions must be explicitly taken into account when interpreting adenosine C2 R1 rates in terms of motional models for large RNAs.
Collapse
Affiliation(s)
- Lukasz T Olenginski
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, MD, 20742, USA
| | - Theodore K Dayie
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, MD, 20742, USA.
| |
Collapse
|
13
|
Chemo-enzymatic synthesis of [2-13C, 7-15 N]-ATP for facile NMR analysis of RNA. MONATSHEFTE FUR CHEMIE 2020. [DOI: 10.1007/s00706-020-02667-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
14
|
Zhou G, Chu S, Kohli A, Szoka FC, Gochin M. Biophysical studies of HIV-1 glycoprotein-41 interactions with peptides and small molecules - Effect of lipids and detergents. Biochim Biophys Acta Gen Subj 2020; 1864:129724. [PMID: 32889078 DOI: 10.1016/j.bbagen.2020.129724] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/18/2020] [Accepted: 08/26/2020] [Indexed: 01/30/2023]
Abstract
BACKGROUND The hydrophobic pocket (HP) of HIV-1 glycoprotein-41 ectodomain is defined by two chains of the N-heptad repeat trimer, within the protein-protein interface that mediates 6HB formation. It is a potential target for inhibitors of viral fusion, but its hydrophobic nature and proximity to membrane in situ has precluded ready analysis of inhibitor interactions. METHODS We evaluated the sensitivity of 19F NMR and fluorescence for detecting peptide and small molecule binding to the HP and explored the effect of non-denaturing detergent or phospholipid as cosolvents and potential mimics of the membrane environment surrounding gp41. RESULTS Chemical shifts of aromatic fluorines were found to be sensitive to changes in the hydrogen bonding network that occurred when inhibitors transitioned from solvent into the HP or into ordered detergent micelles. Fluorescence intensities and emission maxima of autofluorescent compounds responded to changes in the local environment. CONCLUSIONS Gp41 - ligand binding occurred under all conditions, but was diminished in the presence of detergents. NMR and fluorescence studies revealed that dodecylphosphocholine (DPC) was a poor substitute for membrane in this system, while liposomes could mimic the membrane surroundings. GENERAL SIGNIFICANCE Our findings suggest that development of high potency small molecule binders to the HP may be frustrated by competition between binding to the HP and binding to the bilayer membrane.
Collapse
Affiliation(s)
- Guangyan Zhou
- Department of Basic Sciences, College of Osteopathic Medicine, Touro University California, Vallejo, CA 94592, United States of America
| | - Shidong Chu
- Department of Basic Sciences, College of Osteopathic Medicine, Touro University California, Vallejo, CA 94592, United States of America
| | - Aditya Kohli
- Department of Bioengineering and Therapeutic Sciences, UCSF School of Pharmacy, San Francisco, CA 94143, United States of America
| | - Francis C Szoka
- Department of Bioengineering and Therapeutic Sciences, UCSF School of Pharmacy, San Francisco, CA 94143, United States of America; Department of Pharmaceutical Chemistry, UCSF School of Pharmacy, San Francisco, CA 94143, United States of America
| | - Miriam Gochin
- Department of Basic Sciences, College of Osteopathic Medicine, Touro University California, Vallejo, CA 94592, United States of America; Department of Pharmaceutical Chemistry, UCSF School of Pharmacy, San Francisco, CA 94143, United States of America.
| |
Collapse
|
15
|
Structure, interactions and membrane topology of HIV gp41 ectodomain sequences. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183274. [DOI: 10.1016/j.bbamem.2020.183274] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 11/21/2022]
|
16
|
Ghosh U, Weliky DP. 2H nuclear magnetic resonance spectroscopy supports larger amplitude fast motion and interference with lipid chain ordering for membrane that contains β sheet human immunodeficiency virus gp41 fusion peptide or helical hairpin influenza virus hemagglutinin fusion peptide at fusogenic pH. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183404. [PMID: 32585207 DOI: 10.1016/j.bbamem.2020.183404] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/27/2020] [Accepted: 06/19/2020] [Indexed: 01/02/2023]
Abstract
Enveloped viruses are surrounded by a membrane which is obtained from an infected host cell during budding. Infection of a new cell requires joining (fusion) of the virus and cell membranes. This process is mediated by a monotopic viral fusion protein with a large ectodomain outside the virus. The ectodomains of class I enveloped viruses have a N-terminal "fusion peptide" (fp) domain that is critical for fusion and binds to the cell membrane. In this study, 2H NMR spectra are analyzed for deuterated membrane with fp from either HIV gp41 (GP) or influenza hemagglutinin (HA) fusion proteins. In addition, the HAfp samples are studied at more fusogenic pH 5 and less fusogenic pH 7. GPfp adopts intermolecular antiparallel β sheet structure whereas HAfp is a monomeric helical hairpin. The data are obtained for a set of temperatures between 35 and 0 °C using DMPC-d54 lipid with perdeuterated acyl chains. The DMPC has liquid-crystalline (Lα) phase with disordered chains at higher temperature and rippled gel (Pβ') or gel phase (Lβ') with ordered chains at lower temperature. At given temperature T, the no peptide and HAfp, pH 7 samples exhibit similar spectral lineshapes. Spectral broadening with reduced temperature correlates with the transition from Lα to Pβ' and then Lβ' phases. At given T, the lineshapes are narrower for HAfp, pH 5 vs. no peptide and HAfp, pH 7 samples, and even narrower for the GPfp sample. These data support larger-amplitude fast (>105 Hz) lipid acyl chain motion for samples with fusogenic peptides, and peptide interference with chain ordering. The NMR data of the present paper correlate with insertion of these peptides into the hydrocarbon core of the membrane and support a significant fusion contribution from the resultant lipid acyl chain disorder, perhaps because of reduced barriers between the different membrane topologies in the fusion pathway. Membrane insertion and lipid perturbation appear common to both β sheet and helical hairpin peptides.
Collapse
Affiliation(s)
- Ujjayini Ghosh
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
| |
Collapse
|
17
|
Bibow S. Exploring Lipid and Membrane Protein Dynamics Using Lipid-Bilayer Nanodiscs and Solution-State NMR Spectroscopy. Methods Mol Biol 2020; 2127:397-419. [PMID: 32112335 DOI: 10.1007/978-1-0716-0373-4_25] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The relationship of membrane protein function and the surrounding lipid bilayer goes far beyond simple hydrophobic interactions. At least from the 1980s, it is speculated that a certain fluid lipid state may be important not only for the lateral diffusion of membrane proteins (MPs) but also for modulating the catalytic activity of MPs (Lenaz. Bioscience Rep 7 (11):823-837, 1987). Indeed, acyl chain length, hydrophobic mismatch, and lipid headgroups are determinants for enzymatic and transport activities of MPs (Dumas et al. Biochemistry 39(16):4846-4854, 2000; Johannsson et al. Biochim Biophys Acta 641(2):416-421, 1981; Montecucco et al. FEBS Lett 144(1):145-148, 1982; Martens et al. Nat Struct Mol Biol 23(8):744-751, 2016). Moreover, it is speculated that changes in membrane lipid dynamics are important in the field of thermosensation (Vriens J, Nilius B, Voets T, Nat Rev Neurosci 15:573-589, 2014). Atomic insights into lipid-mediated modulation of membrane protein dynamics would therefore provide new insights with the potential to fundamentally extend our understanding on dynamic lipid-protein interdependencies.This chapter describes the expression and purification of nanodiscs assembled from membrane scaffold protein (MSP) as well as the expression and purification of the outer membrane protein X (OmpX). Subsequently, the incorporation of OmpX into MSP-derived nanodiscs is explained in detail. The chapter concludes with the setup of nuclear magnetic resonance (NMR) relaxation experiments and the extraction of relaxation rates for OmpX and the surrounding lipids.
Collapse
Affiliation(s)
- Stefan Bibow
- Biozentrum, University of Basel, Basel, Switzerland.
| |
Collapse
|
18
|
Bibow S. Opportunities and Challenges of Backbone, Sidechain, and RDC Experiments to Study Membrane Protein Dynamics in a Detergent-Free Lipid Environment Using Solution State NMR. Front Mol Biosci 2019; 6:103. [PMID: 31709261 PMCID: PMC6823230 DOI: 10.3389/fmolb.2019.00103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 09/19/2019] [Indexed: 12/22/2022] Open
Abstract
Whereas solution state NMR provided a wealth of information on the dynamics landscape of soluble proteins, only few studies have investigated membrane protein dynamics in a detergent-free lipid environment. Recent developments of smaller nanodiscs and other lipid-scaffolding polymers, such as styrene maleic acid (SMA), however, open new and promising avenues to explore the function-dynamics relationship of membrane proteins as well as between membrane proteins and their surrounding lipid environment. Favorably sized lipid-bilayer nanodiscs, established membrane protein reconstitution protocols and sophisticated solution NMR relaxation methods probing dynamics over a wide range of timescales will eventually reveal unprecedented lipid-membrane protein interdependencies that allow us to explain things we have not been able to explain so far. In particular, methyl group dynamics resulting from CEST, CPMG, ZZ exchange, and RDC experiments are expected to provide new and surprising insights due to their proximity to lipids, their applicability in large 100+ kDa assemblies and their simple labeling due to the availability of commercial precursors. This review summarizes the recent developments of membrane protein dynamics with a special focus on membrane protein dynamics in lipid-bilayer nanodiscs. Opportunities and challenges of backbone, side chain and RDC dynamics applied to membrane proteins are discussed. Solution-state NMR and lipid nanodiscs bear great potential to change our molecular understanding of lipid-membrane protein interactions.
Collapse
Affiliation(s)
- Stefan Bibow
- Biozentrum, University of Basel, Basel, Switzerland
| |
Collapse
|
19
|
Lee M, Morgan CA, Hong M. Fully hydrophobic HIV gp41 adopts a hemifusion-like conformation in phospholipid bilayers. J Biol Chem 2019; 294:14732-14744. [PMID: 31409642 DOI: 10.1074/jbc.ra119.009542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/04/2019] [Indexed: 11/06/2022] Open
Abstract
The HIV envelope glycoprotein mediates virus entry into target cells by fusing the virus lipid envelope with the cell membrane. This process requires large-scale conformational changes of the fusion protein gp41. Current understanding of the mechanisms with which gp41 induces membrane merger is limited by the fact that the hydrophobic N-terminal fusion peptide (FP) and C-terminal transmembrane domain (TMD) of the protein are challenging to characterize structurally in the lipid bilayer. Here we have expressed a gp41 construct that contains both termini, including the FP, the fusion peptide-proximal region (FPPR), the membrane-proximal external region (MPER), and the TMD. These hydrophobic domains are linked together by a shortened water-soluble ectodomain. We reconstituted this "short NC" gp41 into a virus-mimetic lipid membrane and conducted solid-state NMR experiments to probe the membrane-bound conformation and topology of the protein. 13C chemical shifts indicate that the C-terminal MPER-TMD is predominantly α-helical, whereas the N-terminal FP-FPPR exhibits β-sheet character. Water and lipid 1H polarization transfer to the protein revealed that the TMD is well-inserted into the lipid bilayer, whereas the FPPR and MPER are exposed to the membrane surface. Importantly, correlation signals between the FP-FPPR and the MPER are observed, providing evidence that the ectodomain is sufficiently collapsed to bring the N- and C-terminal hydrophobic domains into close proximity. These results support a hemifusion-like model of the short NC gp41 in which the ectodomain forms a partially folded hairpin that places the FPPR and MPER on the opposing surfaces of two lipid membranes.
Collapse
Affiliation(s)
- Myungwoon Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Chloe A Morgan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
20
|
Ranaweera A, Ratnayake PU, Ekanayaka EAP, Declercq R, Weliky DP. Hydrogen-Deuterium Exchange Supports Independent Membrane-Interfacial Fusion Peptide and Transmembrane Domains in Subunit 2 of Influenza Virus Hemagglutinin Protein, a Structured and Aqueous-Protected Connection between the Fusion Peptide and Soluble Ectodomain, and the Importance of Membrane Apposition by the Trimer-of-Hairpins Structure. Biochemistry 2019; 58:2432-2446. [PMID: 31008587 DOI: 10.1021/acs.biochem.8b01272] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The influenza virus hemagglutinin (HA) protein has HA1 and HA2 subunits, which form an initial complex. HA1's bind host cell sialic acids, which triggers endocytosis, HA1/HA2 separation, and HA2-mediated fusion between virus and endosome membranes. We report hydrogen-deuterium exchange mass spectrometry (HDX-MS) on the HA2 subunit without HA1. HA2 contains the fusion peptide (FP), soluble ectodomain (SE), transmembrane domain (TM), and endodomain. FP is a monomer by itself, while SE is a trimer of hairpins that includes an interior bundle of residue 38-105 helices, turns, and residue 154-178 strands packed antiparallel to the bundle. FP and TM extend from the same side of the SE hairpin, and fusion models often depict a FP/TM complex with membrane traversal of both domains that is important for membrane pore expansion. The HDX-MS data of this study do not support this complex and instead support independent FP and TM with respective membrane-interfacial and traversal locations. The data also show a low level of aqueous exposure of the 22-38 segment, consistent with retention of the 23-35 antiparallel β sheet observed in the initial HA1/HA2 complex. We propose the β sheet as a semirigid connector between FP and SE that enables close membrane apposition prior to fusion. The I173E mutant exhibits greater exchange for residues 22-69 and 150-191, consistent with dissociation of SE C-terminal strands from interior N-helices. Similar trends are observed for the G1E mutant as well as less exchange for G1E FP. Fusion is highly impaired with either mutant, which correlates with reduced membrane apposition and, for G1E, FP binding to SE rather than the target membrane.
Collapse
Affiliation(s)
- Ahinsa Ranaweera
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Punsisi U Ratnayake
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - E A Prabodha Ekanayaka
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Robin Declercq
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - David P Weliky
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| |
Collapse
|
21
|
Structural dynamics and transient lipid binding of synaptobrevin-2 tune SNARE assembly and membrane fusion. Proc Natl Acad Sci U S A 2019; 116:8699-8708. [PMID: 30975750 PMCID: PMC6500178 DOI: 10.1073/pnas.1813194116] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The vesicular membrane protein synaptobrevin-2 (syb-2) plays an important role in vesicular membrane fusion at the neuronal synapse by participating in the dynamic formation of the SNARE complex. Here, by a combination of solution-state NMR and fluorescence spectroscopy, we find that syb-2 in its prefusion form, before forming the SNARE complex, shows high internal flexibility, characteristic for an intrinsically disordered protein (IDP). But it also reveals an increasing rigidity from the N to C terminus that correlates with an observed increase in lipid binding affinity as well as the known increased rate for C-terminal compared with N-terminal SNARE zippering. This provides a mechanistic perspective on how an IDP and its lipid interactions can lower the energy barrier for membrane fusion. Intrinsically disordered proteins (IDPs) and their conformational transitions play an important role in neurotransmitter release at the neuronal synapse. Here, the SNARE proteins are essential by forming the SNARE complex that drives vesicular membrane fusion. While it is widely accepted that the SNARE proteins are intrinsically disordered in their monomeric prefusion form, important mechanistic aspects of this prefusion conformation and its lipid interactions, before forming the SNARE complex, are not fully understood at the molecular level and remain controversial. Here, by a combination of NMR and fluorescence spectroscopy methods, we find that vesicular synaptobrevin-2 (syb-2) in its monomeric prefusion conformation shows high flexibility, characteristic for an IDP, but also a high dynamic range and increasing rigidity from the N to C terminus. The gradual increase in rigidity correlates with an increase in lipid binding affinity from the N to C terminus. It could also explain the increased rate for C-terminal SNARE zippering, known to be faster than N-terminal SNARE zippering. Also, the syb-2 SNARE motif and, in particular, the linker domain show transient and weak membrane binding, characterized by a high off-rate and low (millimolar) affinity. The transient membrane binding of syb-2 may compensate for the repulsive forces between the two membranes and/or the SNARE motifs and the membranes, helping to destabilize the hydrophilic-hydrophobic boundary in the bilayer. Therefore, we propose that optimum flexibility and membrane binding of syb-2 regulate SNARE assembly and minimize repulsive forces during membrane fusion.
Collapse
|
22
|
Liao SY, Lee M, Hong M. Interplay between membrane curvature and protein conformational equilibrium investigated by solid-state NMR. J Struct Biol 2019; 206:20-28. [PMID: 29501472 PMCID: PMC6119545 DOI: 10.1016/j.jsb.2018.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 02/19/2018] [Accepted: 02/26/2018] [Indexed: 11/28/2022]
Abstract
Many membrane proteins sense and induce membrane curvature for function, but structural information about how proteins modulate their structures to cause membrane curvature is sparse. We review our recent solid-state NMR studies of two virus membrane proteins whose conformational equilibrium is tightly coupled to membrane curvature. The influenza M2 proton channel has a drug-binding site in the transmembrane (TM) pore. Previous chemical shift data indicated that this pore-binding site is lost in an M2 construct that contains the TM domain and a curvature-inducing amphipathic helix. We have now obtained chemical shift perturbation, protein-drug proximity, and drug orientation data that indicate that the pore-binding site is restored when the full cytoplasmic domain is present. This finding indicates that the curvature-inducing amphipathic helix distorts the TM structure to interfere with drug binding, while the cytoplasmic tail attenuates this effect. In the second example, we review our studies of a parainfluenza virus fusion protein that merges the cell membrane and the virus envelope during virus entry. Chemical shifts of two hydrophobic domains of the protein indicate that both domains have membrane-dependent backbone conformations, with the β-strand structure dominating in negative-curvature phosphatidylethanolamine (PE) membranes. 31P NMR spectra and 1H-31P correlation spectra indicate that the β-strand-rich conformation induces saddle-splay curvature to PE membranes and dehydrates them, thus stabilizing the hemifusion state. These results highlight the indispensable role of solid-state NMR to simultaneously determine membrane protein structures and characterize the membrane curvature in which these protein structures exist.
Collapse
Affiliation(s)
- Shu Y Liao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Myungwoon Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
| |
Collapse
|
23
|
Kumari P, Frey L, Sobol A, Lakomek NA, Riek R. 15N transverse relaxation measurements for the characterization of µs-ms dynamics are deteriorated by the deuterium isotope effect on 15N resulting from solvent exchange. JOURNAL OF BIOMOLECULAR NMR 2018; 72:125-137. [PMID: 30306288 DOI: 10.1007/s10858-018-0211-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 10/03/2018] [Indexed: 06/08/2023]
Abstract
15N R2 relaxation measurements are key for the elucidation of the dynamics of both folded and intrinsically disordered proteins (IDPs). Here we show, on the example of the intrinsically disordered protein α-synuclein and the folded domain PDZ2, that at physiological pH and near physiological temperatures amide-water exchange can severely skew Hahn-echo based 15N R2 relaxation measurements as well as low frequency data points in CPMG relaxation dispersion experiments. The nature thereof is the solvent exchange with deuterium in the sample buffer, which modulates the 15N chemical shift tensor via the deuterium isotope effect, adding to the apparent relaxation decay which leads to systematic errors in the relaxation data. This results in an artificial increase of the measured apparent 15N R2 rate constants-which should not be mistaken with protein inherent chemical exchange contributions, Rex, to 15N R2. For measurements of 15N R2 rate constants of IDPs and folded proteins at physiological temperatures and pH, we recommend therefore the use of a very low D2O molar fraction in the sample buffer, as low as 1%, or the use of an external D2O reference along with a modified 15N R2 Hahn-echo based experiment. This combination allows for the measurement of Rex contributions to 15N R2 originating from conformational exchange in a time window from µs to ms.
Collapse
Affiliation(s)
- Pratibha Kumari
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Lukas Frey
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Alexander Sobol
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Nils-Alexander Lakomek
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland.
| | - Roland Riek
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland.
| |
Collapse
|
24
|
Si L, Meng K, Tian Z, Sun J, Li H, Zhang Z, Soloveva V, Li H, Fu G, Xia Q, Xiao S, Zhang L, Zhou D. Triterpenoids manipulate a broad range of virus-host fusion via wrapping the HR2 domain prevalent in viral envelopes. SCIENCE ADVANCES 2018; 4:eaau8408. [PMID: 30474060 PMCID: PMC6248931 DOI: 10.1126/sciadv.aau8408] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/24/2018] [Indexed: 05/19/2023]
Abstract
A trimer-of-hairpins motif has been identified in triggering virus-cell fusion within a variety of viral envelopes. Chemically manipulating such a motif represents current repertoire of viral fusion inhibitors. Here, we report that triterpenoids, a class of natural products, antagonize this trimer-of-hairpins via its constitutive heptad repeat-2 (HR2), a prevalent α-helical coil in class I viral fusion proteins. Triterpenoids inhibit the entry of Ebola, Marburg, HIV, and influenza A viruses with distinct structure-activity relationships. Specifically, triterpenoid probes capture the viral envelope via photocrosslinking HR2. Profiling the Ebola HR2-triterpenoid interactions using amino acid substitution, surface plasmon resonance, and nuclear magnetic resonance revealed six residues accessible to triterpenoids, leading to wrapping of the hydrophobic helix and blocking of the HR1-HR2 interaction critical in the trimer-of-hairpins formation. This finding was also observed in the envelopes of HIV and influenza A viruses and might potentially extend to a broader variety of viruses, providing a mechanistic insight into triterpenoid-mediated modulation of viral fusion.
Collapse
Affiliation(s)
- Longlong Si
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Kun Meng
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Zhenyu Tian
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Jiaqi Sun
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Huiqiang Li
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Ziwei Zhang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Veronica Soloveva
- U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA
| | - Haiwei Li
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Ge Fu
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Qing Xia
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Sulong Xiao
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Lihe Zhang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
| | - Demin Zhou
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China
- Corresponding author.
| |
Collapse
|
25
|
Frey L, Hiller S, Riek R, Bibow S. Lipid- and Cholesterol-Mediated Time-Scale-Specific Modulation of the Outer Membrane Protein X Dynamics in Lipid Bilayers. J Am Chem Soc 2018; 140:15402-15411. [PMID: 30289706 DOI: 10.1021/jacs.8b09188] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Membrane protein function fundamentally depends on lipid-bilayer fluidity and the composition of the biological membrane. Although dynamic interdependencies between membrane proteins and the surrounding lipids are suspected, a detailed description is still missing. To uncover lipid-modulated membrane protein backbone dynamics, time-scale-specific NMR relaxation experiments with residue-resolution were recorded. The data revealed that lipid order, modified either biochemically or biophysically, changes the dynamics of the immersed membrane protein in a specific and time-scale-dependent manner. A temperature-dependent dynamics analysis furthermore suggests a direct coupling between lipid and protein dynamics in the picosecond-nanosecond, microsecond, and millisecond time scales, caused by the lipid's trans-gauche isomerization, the segmental and rotational motion of lipids, and the fluidity of the lipid phase, respectively. These observations provide evidence of a direct modulatory capability of the membrane to regulate protein function through lipid dynamics ranging from picoseconds to milliseconds.
Collapse
Affiliation(s)
- Lukas Frey
- Laboratory for Physical Chemistry , ETH Zurich , 8093 Zurich , Switzerland
| | | | - Roland Riek
- Laboratory for Physical Chemistry , ETH Zurich , 8093 Zurich , Switzerland
| | - Stefan Bibow
- Biozentrum , University of Basel , 4056 Basel , Switzerland
| |
Collapse
|
26
|
Ranaweera A, Ratnayake PU, Weliky DP. The Stabilities of the Soluble Ectodomain and Fusion Peptide Hairpins of the Influenza Virus Hemagglutinin Subunit II Protein Are Positively Correlated with Membrane Fusion. Biochemistry 2018; 57:5480-5493. [PMID: 30141905 DOI: 10.1021/acs.biochem.8b00764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cellular entry of influenza virus is mediated by the viral protein hemagglutinin (HA), which forms an initial complex of three HA1 and three HA2 subunits. Each HA2 includes a fusion peptide (FP), a soluble ectodomain (SE), and a transmembrane domain. HA1 binds to cellular sialic acids, followed by virus endocytosis, pH reduction, dissociation of HA1, and structural rearrangement of HA2 into a final trimer-of-SE hairpins. A decrease in pH also triggers HA2-mediated virus/endosome membrane fusion. SE hairpins have an interior parallel helical bundle and C-terminal strands in the grooves of the exterior of the bundle. FPs are separate helical hairpins. This study compares wild-type HA2 (WT-HA2) with G1E(FP) and I173E(SE strand) mutants. WT-HA2 induces vesicle fusion at pH 5.0, whereas the extent of fusion is greatly reduced for both mutants. Circular dichroism for HA2 and FHA2≡FP+SE constructs shows dramatic losses of stability for the mutants, including a Tm reduced by 40 °C for I173E-FHA2. This is evidence of destabilization of SE hairpins via dissociation of strands from the helical bundle, which is also supported by larger monomer fractions for mutant versus WT proteins. The G1E mutant may have disrupted FP hairpins, with consequent non-native FP binding to dissociated SE strands. It is commonly proposed that free energy released by the HA2 structural rearrangement catalyzes HA-mediated fusion. This study supports an alternate mechanistic model in which fusion is preceded by FP insertion in the target membrane and formation of the final SE hairpin. Less fusion by the mutants is due to the loss of hairpin stability and consequent reduced level of membrane apposition of the virus and target membranes.
Collapse
Affiliation(s)
- Ahinsa Ranaweera
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Punsisi U Ratnayake
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - David P Weliky
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| |
Collapse
|
27
|
Kwon B, Lee M, Waring AJ, Hong M. Oligomeric Structure and Three-Dimensional Fold of the HIV gp41 Membrane-Proximal External Region and Transmembrane Domain in Phospholipid Bilayers. J Am Chem Soc 2018; 140:8246-8259. [PMID: 29888593 DOI: 10.1021/jacs.8b04010] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The HIV-1 glycoprotein, gp41, mediates fusion of the virus lipid envelope with the target cell membrane during virus entry into cells. Despite extensive studies of this protein, inconsistent and contradictory structural information abounds in the literature about the C-terminal membrane-interacting region of gp41. This C-terminal region contains the membrane-proximal external region (MPER), which harbors the epitopes for four broadly neutralizing antibodies, and the transmembrane domain (TMD), which anchors the protein to the virus lipid envelope. Due to the difficulty of crystallizing and solubilizing the MPER-TMD, most structural studies of this functionally important domain were carried out using truncated peptides either in the absence of membrane-mimetic solvents or bound to detergents and lipid bicelles. To determine the structural architecture of the MPER-TMD in the native environment of lipid membranes, we have now carried out a solid-state NMR study of the full MPER-TMD segment bound to cholesterol-containing phospholipid bilayers. 13C chemical shifts indicate that the majority of the peptide is α-helical, except for the C-terminus of the TMD, which has moderate β-sheet character. Intermolecular 19F-19F distance measurements of singly fluorinated peptides indicate that the MPER-TMD is trimerized in the virus-envelope mimetic lipid membrane. Intramolecular 13C-19F distance measurements indicate the presence of a turn between the MPER helix and the TMD helix. This is supported by lipid-peptide and water-peptide 2D 1H-13C correlation spectra, which indicate that the MPER binds to the membrane surface whereas the TMD spans the bilayer. Together, these data indicate that full-length MPER-TMD assembles into a trimeric helix-turn-helix structure in lipid membranes. We propose that the turn between the MPER and TMD may be important for inducing membrane defects in concert with negative-curvature lipid components such as cholesterol and phosphatidylethanolamine, while the surface-bound MPER helix may interact with N-terminal segments of the protein during late stages of membrane fusion.
Collapse
Affiliation(s)
- Byungsu Kwon
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
| | - Myungwoon Lee
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
| | - Alan J Waring
- Department of Medicine , Harbor-UCLA Medical Center , 1000 West Carson Street, Building RB2 , Torrance , California 90502 , United States
| | - Mei Hong
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
| |
Collapse
|
28
|
Schroeder S, Kaufman JD, Grunwald M, Walla PJ, Lakomek NA, Wingfield PT. HIV-1 gp41 transmembrane oligomerization monitored by FRET and FCS. FEBS Lett 2018; 592:939-948. [PMID: 29453892 DOI: 10.1002/1873-3468.13010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/21/2018] [Accepted: 02/11/2018] [Indexed: 11/08/2022]
Abstract
The HIV-1 envelope gp120/gp41 trimer mediates viral membrane fusion. After cluster of differentiation-4 recognition, gp120 detaches from the virus, exposing gp41 which triggers fusion. During the fusion process, gp41 may not remain trimeric, which could have functional importance. Here, we probe the reversible association of full length gp41 (minus the cytoplasmic domain) in detergent micelles (with probes attached to transmembrane domain) by fluorescence resonance energy transfer (FRET) with a μm dissociation constant. This is compared with other methods. A gp41-targeted fusion inhibitor must interfere with this transition, and monomeric, partially monomeric or trimeric states all present potential binding epitopes. The gp41 self-association is a valid drug target model and FRET, a potential high-throughput assay system, could be used to screen drug libraries.
Collapse
Affiliation(s)
| | - Joshua D Kaufman
- Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, MD, USA
| | | | - Peter J Walla
- Institute for Physical and Theoretical Chemistry, Technical University Braunschweig, Germany
| | - Nils-Alexander Lakomek
- Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences (D-CHAB), ETH Zurich, Switzerland
| | - Paul T Wingfield
- Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
29
|
Oakes V, Torralba J, Rujas E, Nieva JL, Domene C, Apellaniz B. Exposure of the HIV-1 broadly neutralizing antibody 10E8 MPER epitope on the membrane surface by gp41 transmembrane domain scaffolds. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1259-1271. [PMID: 29477358 DOI: 10.1016/j.bbamem.2018.02.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 01/30/2018] [Accepted: 02/20/2018] [Indexed: 12/27/2022]
Abstract
The 10E8 antibody achieves near-pan neutralization of HIV-1 by targeting the remarkably conserved gp41 membrane-proximal external region (MPER) and the connected transmembrane domain (TMD) of the HIV-1 envelope glycoprotein (Env). Thus, recreating the structure that generates 10E8-like antibodies is a major goal of the rational design of anti-HIV vaccines. Unfortunately, high-resolution information of this segment in the native Env is lacking, limiting our understanding of the behavior of the crucial 10E8 epitope residues. In this report, two sequences, namely, MPER-TMD1 (gp41 residues 671-700) and MPER-TMD2 (gp41 residues 671-709) were compared both experimentally and computationally, to assess the TMD as a potential membrane integral scaffold for the 10E8 epitope. These sequences were selected to represent a minimal (MPER-TMD1) or full-length (MPER-TMD2) TMD membrane anchor according to mutagenesis results reported by Yue et al. (2009) J. Virol. 83, 11,588. Immunochemical assays revealed that MPER-TMD1, but not MPER-TMD2, effectively exposed the MPER C-terminal stretch, harboring the 10E8 epitope on the surface of phospholipid bilayers containing a cholesterol concentration equivalent to that of the viral envelope. Molecular dynamics simulations, using the recently resolved TMD trimer structure combined with the MPER in a cholesterol-enriched model membrane confirmed these results and provided an atomistic mechanism of epitope exposure which revealed that TMD truncation at position A700 combined with N-terminal addition of lysine residues positively impacts epitope exposure. Overall, these results provide crucial insights into the design of effective MPER-TMD derived immunogens.
Collapse
Affiliation(s)
- Victoria Oakes
- Department of Chemistry, Britannia House, 7 Trinity Street, King's College London, London SE1 1DB, UK; Department of Chemistry, 1 South Building, Claverton Down Road, University of Bath, Bath BA2 7AY, UK
| | - Johana Torralba
- Biofisika Institute (CSIC, UPV/EHU), Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - Edurne Rujas
- Biofisika Institute (CSIC, UPV/EHU), Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - José L Nieva
- Biofisika Institute (CSIC, UPV/EHU), Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - Carmen Domene
- Department of Chemistry, 1 South Building, Claverton Down Road, University of Bath, Bath BA2 7AY, UK; Chemistry Research Laboratory, Mansfield Road, University of Oxford, Oxford OX1 3TA, UK.
| | - Beatriz Apellaniz
- Biofisika Institute (CSIC, UPV/EHU), Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain.
| |
Collapse
|
30
|
Liang S, Ratnayake PU, Keinath C, Jia L, Wolfe R, Ranaweera A, Weliky DP. Efficient Fusion at Neutral pH by Human Immunodeficiency Virus gp41 Trimers Containing the Fusion Peptide and Transmembrane Domains. Biochemistry 2018; 57:1219-1235. [PMID: 29345922 DOI: 10.1021/acs.biochem.7b00753] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human immunodeficiency virus (HIV) is membrane-enveloped, and an initial infection step is joining/fusion of viral and cell membranes. This step is catalyzed by gp41, which is a single-pass integral viral membrane protein. The protein contains an ∼170-residue ectodomain located outside the virus that is important for fusion and includes the fusion peptide (FP), N-helix, loop, C-helix, and viral membrane-proximal external region (MPER). The virion initially has noncovalent complexes between three gp41 ectodomains and three gp120 proteins. A gp120 contains ∼500 residues and functions to identify target T-cells and macrophages via binding to specific protein receptors of the target cell membrane. gp120 moves away from the gp41 ectodomain, and the ectodomain is thought to bind to the target cell membrane and mediate membrane fusion. The secondary and tertiary structures of the ectodomain are different in the initial complex with gp120 and the final state without gp120. There is not yet imaging of gp41 during fusion, so the temporal relationship between the gp41 and membrane structures is not known. This study describes biophysical and functional characterization of large gp41 constructs that include the ectodomain and transmembrane domain (TM). Significant fusion is observed of both neutral and anionic vesicles at neutral pH, which reflects the expected conditions of HIV/cell fusion. Fusion is enhanced by the FP, which in HIV/cell fusion likely contacts the host membrane, and the MPER and TM, which respectively interfacially contact and traverse the HIV membrane. Initial contact with vesicles is made by protein trimers that are in a native oligomeric state that reflects the initial complex with gp120 and also is commonly observed for the ectodomain without gp120. Circular dichroism data support helical structure for the N-helix, C-helix, and MPER and nonhelical structure for the FP and loop. Distributions of monomer, trimer, and hexamer states are observed by size-exclusion chromatography (SEC), with dependences on solubilizing detergent and construct. These SEC and other data are integrated into a refined working model of HIV/cell fusion that includes dissociation of the ectodomain into gp41 monomers followed by folding into hairpins that appose the two membranes, and subsequent fusion catalysis by trimers and hexamers of hairpins. The monomer and oligomer gp41 states may therefore satisfy dual requirements for HIV entry of membrane apposition and fusion.
Collapse
Affiliation(s)
- S Liang
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - P U Ratnayake
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - C Keinath
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - L Jia
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - R Wolfe
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - A Ranaweera
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - D P Weliky
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| |
Collapse
|
31
|
Srb P, Nováček J, Kadeřávek P, Rabatinová A, Krásný L, Žídková J, Bobálová J, Sklenář V, Žídek L. Triple resonance ¹⁵Ν NMR relaxation experiments for studies of intrinsically disordered proteins. JOURNAL OF BIOMOLECULAR NMR 2017; 69:133-146. [PMID: 29071460 DOI: 10.1007/s10858-017-0138-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 09/26/2017] [Indexed: 06/07/2023]
Abstract
Description of protein dynamics is known to be essential in understanding their function. Studies based on a well established [Formula: see text] NMR relaxation methodology have been applied to a large number of systems. However, the low dispersion of [Formula: see text] chemical shifts very often observed within intrinsically disordered proteins complicates utilization of standard 2D HN correlated spectra because a limited number of amino acids can be characterized. Here we present a suite of triple resonance HNCO-type NMR experiments for measurements of five [Formula: see text] relaxation parameters ([Formula: see text], [Formula: see text], NOE, cross-correlated relaxation rates [Formula: see text] and [Formula: see text]) in doubly [Formula: see text],[Formula: see text]-labeled proteins. We show that the third spectral dimension combined with non-uniform sampling provides relaxation rates for almost all residues of a protein with extremely poor chemical shift dispersion, the C terminal domain of [Formula: see text]-subunit of RNA polymerase from Bacillus subtilis. Comparison with data obtained using a sample labeled by [Formula: see text] only showed that the presence of [Formula: see text] has a negligible effect on [Formula: see text], [Formula: see text], and on the cross-relaxation rate (calculated from NOE and [Formula: see text]), and that these relaxation rates can be used to calculate accurate spectral density values. Partially [Formula: see text]-labeled sample was used to test if the observed increase of [Formula: see text] [Formula: see text] in the presence of [Formula: see text] corresponds to the [Formula: see text] dipole-dipole interactions in the [Formula: see text],[Formula: see text]-labeled sample.
Collapse
Affiliation(s)
- Pavel Srb
- Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo náměstí, 542/2, 166 10, Praha 6, Czech Republic
| | - Jiří Nováček
- Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic
| | - Pavel Kadeřávek
- Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic
| | - Alžbeta Rabatinová
- Laboratory of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic v.v.i., Videňská 1083, 142 20, Prague, Czech Republic
| | - Libor Krásný
- Laboratory of Molecular Genetics of Bacteria, Institute of Microbiology, Academy of Sciences of the Czech Republic v.v.i., Videňská 1083, 142 20, Prague, Czech Republic
| | - Jitka Žídková
- Institute of Analytical Chemistry of the Czech Academy of Sciences v.v.i., Veveří 97, 602 00, Brno, Czech Republic
| | - Janette Bobálová
- Institute of Analytical Chemistry of the Czech Academy of Sciences v.v.i., Veveří 97, 602 00, Brno, Czech Republic
| | - Vladimír Sklenář
- Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic
| | - Lukáš Žídek
- Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic.
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 625 00, Brno, Czech Republic.
| |
Collapse
|
32
|
Ikeya T, Ban D, Lee D, Ito Y, Kato K, Griesinger C. Solution NMR views of dynamical ordering of biomacromolecules. Biochim Biophys Acta Gen Subj 2017; 1862:287-306. [PMID: 28847507 DOI: 10.1016/j.bbagen.2017.08.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/22/2017] [Accepted: 08/24/2017] [Indexed: 01/01/2023]
Abstract
BACKGROUND To understand the mechanisms related to the 'dynamical ordering' of macromolecules and biological systems, it is crucial to monitor, in detail, molecular interactions and their dynamics across multiple timescales. Solution nuclear magnetic resonance (NMR) spectroscopy is an ideal tool that can investigate biophysical events at the atomic level, in near-physiological buffer solutions, or even inside cells. SCOPE OF REVIEW In the past several decades, progress in solution NMR has significantly contributed to the elucidation of three-dimensional structures, the understanding of conformational motions, and the underlying thermodynamic and kinetic properties of biomacromolecules. This review discusses recent methodological development of NMR, their applications and some of the remaining challenges. MAJOR CONCLUSIONS Although a major drawback of NMR is its difficulty in studying the dynamical ordering of larger biomolecular systems, current technologies have achieved considerable success in the structural analysis of substantially large proteins and biomolecular complexes over 1MDa and have characterised a wide range of timescales across which biomolecular motion exists. While NMR is well suited to obtain local structure information in detail, it contributes valuable and unique information within hybrid approaches that combine complementary methodologies, including solution scattering and microscopic techniques. GENERAL SIGNIFICANCE For living systems, the dynamic assembly and disassembly of macromolecular complexes is of utmost importance for cellular homeostasis and, if dysregulated, implied in human disease. It is thus instructive for the advancement of the study of the dynamical ordering to discuss the potential possibilities of solution NMR spectroscopy and its applications. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato.
Collapse
Affiliation(s)
- Teppei Ikeya
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji, Tokyo 192-0373, Japan; CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
| | - David Ban
- Department of Medicine, James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Donghan Lee
- Department of Medicine, James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Yutaka Ito
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji, Tokyo 192-0373, Japan; CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Koichi Kato
- Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan; Graduate School of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori 3-1, Mizuho-ku, Nagoya 467-8603, Japan
| | - Christian Griesinger
- Department of Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany.
| |
Collapse
|
33
|
Pérez Y, Gómara MJ, Yuste E, Gómez-Gutierrez P, Pérez JJ, Haro I. Structural Study of a New HIV-1 Entry Inhibitor and Interaction with the HIV-1 Fusion Peptide in Dodecylphosphocholine Micelles. Chemistry 2017; 23:11703-11713. [DOI: 10.1002/chem.201702531] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Yolanda Pérez
- Nuclear Magnetic Resonance Facility; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
| | - Maria José Gómara
- Unit of Synthesis and Biomedical Applications of Peptides; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
| | - Eloísa Yuste
- Department of Chemical Engineering (ETSEIB); Universitat Politecnica de Catalunya; 08034 Barcelona Spain
- Present address: AIDS Immunopathology Unit; Centro Nacional Microbiología; Instituto de Salud Carlos III; 28029 Madrid Spain
| | | | | | - Isabel Haro
- Unit of Synthesis and Biomedical Applications of Peptides; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
| |
Collapse
|
34
|
Bibow S, Polyhach Y, Eichmann C, Chi CN, Kowal J, Albiez S, McLeod RA, Stahlberg H, Jeschke G, Güntert P, Riek R. Solution structure of discoidal high-density lipoprotein particles with a shortened apolipoprotein A-I. Nat Struct Mol Biol 2016; 24:187-193. [DOI: 10.1038/nsmb.3345] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/29/2016] [Indexed: 01/08/2023]
|
35
|
Yao H, Lee M, Liao SY, Hong M. Solid-State Nuclear Magnetic Resonance Investigation of the Structural Topology and Lipid Interactions of a Viral Fusion Protein Chimera Containing the Fusion Peptide and Transmembrane Domain. Biochemistry 2016; 55:6787-6800. [DOI: 10.1021/acs.biochem.6b00568] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hongwei Yao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Myungwoon Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Shu-Yu Liao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| |
Collapse
|
36
|
Frey L, Lakomek NA, Riek R, Bibow S. Micelles, Bicelles, and Nanodiscs: Comparing the Impact of Membrane Mimetics on Membrane Protein Backbone Dynamics. Angew Chem Int Ed Engl 2016; 56:380-383. [PMID: 27882643 PMCID: PMC6680326 DOI: 10.1002/anie.201608246] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 09/29/2016] [Indexed: 11/10/2022]
Abstract
Detergents are often used to investigate the structure and dynamics of membrane proteins. Whereas the structural integrity seems to be preserved in detergents for many membrane proteins, their functional activity is frequently compromised, but can be restored in a lipid environment. Herein we show with per‐residue resolution that while OmpX forms a stable β‐barrel in DPC detergent micelles, DHPC/DMPC bicelles, and DMPC nanodiscs, the pico‐ to nanosecond and micro‐ to millisecond motions differ substantially between the detergent and lipid environment. In particular for the β‐strands, there is pronounced dynamic variability in the lipid environment, which appears to be suppressed in micelles. This unexpected complex and membrane‐mimetic‐dependent dynamic behavior indicates that the frequent loss of membrane protein activity in detergents might be related to reduced internal dynamics and that membrane protein activity correlates with lipid flexibility.
Collapse
Affiliation(s)
- Lukas Frey
- Laboratory for Physical Chemistry, ETH Zurich, 8093, Zurich, Switzerland
| | | | - Roland Riek
- Laboratory for Physical Chemistry, ETH Zurich, 8093, Zurich, Switzerland
| | - Stefan Bibow
- Laboratory for Physical Chemistry, ETH Zurich, 8093, Zurich, Switzerland
| |
Collapse
|
37
|
Frey L, Lakomek N, Riek R, Bibow S. Mizellen, Bizellen und Nanoscheiben: Einfluss von membranimitierenden Umgebungen auf die Membranproteindynamik. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201608246] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Lukas Frey
- Laboratorium für Physikalische Chemie ETH Zürich 8093 Zürich Schweiz
| | | | - Roland Riek
- Laboratorium für Physikalische Chemie ETH Zürich 8093 Zürich Schweiz
| | - Stefan Bibow
- Laboratorium für Physikalische Chemie ETH Zürich 8093 Zürich Schweiz
| |
Collapse
|
38
|
Sapienza PJ, Lee AL. Widespread Perturbation of Function, Structure, and Dynamics by a Conservative Single-Atom Substitution in Thymidylate Synthase. Biochemistry 2016; 55:5702-5713. [PMID: 27649373 DOI: 10.1021/acs.biochem.6b00838] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thymidylate synthase (TSase) is responsible for synthesizing the sole de novo source of dTMP in all organisms. TSase is a drug target, and as such, it has been well studied in terms of both structure and reaction mechanism. Cysteine 146 in Escherichia coli TSase is universally conserved because it serves as the nucleophile in the enzyme mechanism. Here we use the C146S mutation to probe the role of the sulfur atom in early events in the catalytic cycle beyond serving as the nucleophile. Surprisingly, the single-atom substitution severely decreases substrate binding affinity, and the unfavorable ΔΔG°bind is comprised of roughly equal enthalpic and entropic components at 25 °C. Chemical shifts in the free and dUMP-bound states show the mutation causes perturbations throughout TSase, including regions important for complex stability, in agreement with a less favorable enthalpy change. We measured the nuclear magnetic resonance methyl symmetry axis order parameter (S2axis), a proxy for conformational entropy, for TSase at all vertices of the dUMP binding/C146S mutation thermodynamic cycle and found that the calculated TΔΔS°conf is similar in sign and magnitude to the calorimetric TΔΔS°. Further, we ascribed minor resonances in wild-type-dUMP spectra to a state with a covalent bond between Sγ of C146 and C6 of dUMP and find S2axis values are unaffected by covalent bond formation, indicating this reaction step is neutral with respect to ΔS°conf. Lastly, the C146S mutation allowed us to measure cofactor analog binding by isothermal titration calorimetry without the confounding heat signature of covalent bond formation. Raltitrexed binds free and singly bound TSase with similar affinities, yet the two binding events have different enthalpy changes, providing further evidence of communication between the two active sites.
Collapse
Affiliation(s)
- Paul J Sapienza
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Andrew L Lee
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| |
Collapse
|
39
|
Louis JM, Baber JL, Ghirlando R, Aniana A, Bax A, Roche J. Insights into the Conformation of the Membrane Proximal Regions Critical to the Trimerization of the HIV-1 gp41 Ectodomain Bound to Dodecyl Phosphocholine Micelles. PLoS One 2016; 11:e0160597. [PMID: 27513582 PMCID: PMC4981318 DOI: 10.1371/journal.pone.0160597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/21/2016] [Indexed: 01/06/2023] Open
Abstract
The transitioning of the ectodomain of gp41 from a pre-hairpin to a six-helix bundle conformation is a crucial aspect of virus-cell fusion. To gain insight into the intermediary steps of the fusion process we have studied the pH and dodecyl phosphocholine (DPC) micelle dependent trimer association of gp41 by systematic deletion analysis of an optimized construct termed 17-172 (residues 528 to 683 of Env) that spans the fusion peptide proximal region (FPPR) to the membrane proximal external region (MPER) of gp41, by sedimentation velocity and double electron-electron resonance (DEER) EPR spectroscopy. Trimerization at pH 7 requires the presence of both the FPPR and MPER regions. However, at pH 4, the protein completely dissociates to monomers. DEER measurements reveal a partial fraying of the C-terminal MPER residues in the 17-172 trimer while the other regions, including the FPPR, remain compact. In accordance, truncating nine C-terminal MPER residues (675-683) in the 17-172 construct does not shift the trimer-monomer equilibrium significantly. Thus, in the context of the gp41 ectodomain spanning residues 17-172, trimerization is clearly dependent on FPPR and MPER regions even when the terminal residues of MPER unravel. The antibody Z13e1, which spans both the 2F5 and 4E10 epitopes in MPER, binds to 17-172 with a Kd of 1 ± 0.12 μM. Accordingly, individual antibodies 2F5 and 4E10 also recognize the 17-172 trimer/DPC complex. We propose that binding of the C-terminal residues of MPER to the surface of the DPC micelles models a correct positioning of the trimeric transmembrane domain anchored in the viral membrane.
Collapse
Affiliation(s)
- John M. Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (JL)); (JR)
| | - James L. Baber
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Annie Aniana
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Julien Roche
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, United States of America
- * E-mail: (JL)); (JR)
| |
Collapse
|
40
|
Vo U, Vajpai N, Embrey KJ, Golovanov AP. Dynamic studies of H-Ras•GTPγS interactions with nucleotide exchange factor Sos reveal a transient ternary complex formation in solution. Sci Rep 2016; 6:29706. [PMID: 27412770 PMCID: PMC4944212 DOI: 10.1038/srep29706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 06/21/2016] [Indexed: 11/26/2022] Open
Abstract
The cycling between GDP- and GTP- bound forms of the Ras protein is partly regulated by the binding of Sos. The structural/dynamic behavior of the complex formed between activated Sos and Ras at the point of the functional cycle where the nucleotide exchange is completed has not been described to date. Here we show that solution NMR spectra of H-Ras∙GTPγS mixed with a functional fragment of Sos (SosCat) at a 2:1 ratio are consistent with the formation of a rather dynamic assembly. H-Ras∙GTPγS binding was in fast exchange on the NMR timescale and retained a significant degree of molecular tumbling independent of SosCat, while SosCat also tumbled largely independently of H-Ras. Estimates of apparent molecular weight from both NMR data and SEC-MALS revealed that, at most, only one H-Ras∙GTPγS molecule appears stably bound to Sos. The weak transient interaction between Sos and the second H-Ras∙GTPγS may provide a necessary mechanism for complex dissociation upon the completion of the native GDP → GTP exchange reaction, but also explains measurable GTP → GTP exchange activity of Sos routinely observed in in vitro assays that use fluorescently-labelled analogs of GTP. Overall, the data presents the first dynamic snapshot of Ras functional cycle as controlled by Sos.
Collapse
Affiliation(s)
- Uybach Vo
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
| | - Navratna Vajpai
- AstraZeneca, Discovery Sciences, Mereside, Alderley Park, Cheshire, SK10 4TF, UK
| | - Kevin J Embrey
- AstraZeneca, Discovery Sciences, Mereside, Alderley Park, Cheshire, SK10 4TF, UK
| | - Alexander P Golovanov
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
| |
Collapse
|
41
|
Lakomek NA, Draycheva A, Bornemann T, Wintermeyer W. Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY. Angew Chem Int Ed Engl 2016; 55:9544-7. [PMID: 27346853 PMCID: PMC5094494 DOI: 10.1002/anie.201602905] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/19/2016] [Indexed: 01/18/2023]
Abstract
Integral membrane proteins in bacteria are co‐translationally targeted to the SecYEG translocon for membrane insertion via the signal recognition particle (SRP) pathway. The SRP receptor FtsY and its N‐terminal A domain, which is lacking in any structural model of FtsY, were studied using NMR and fluorescence spectroscopy. The A domain is mainly disordered and highly flexible; it binds to lipids via its N terminus and the C‐terminal membrane targeting sequence. The central A domain binds to the translocon non‐specifically and maintains disorder. Translocon targeting and binding of the A domain is driven by electrostatic interactions. The intrinsically disordered A domain tethers FtsY to the translocon, and because of its flexibility, allows the FtsY NG domain to scan a large area for binding to the NG domain of ribosome‐bound SRP, thereby promoting the formation of the quaternary transfer complex at the membrane.
Collapse
Affiliation(s)
- Nils-Alexander Lakomek
- Department of NMR-based Structural Biology, Max-Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany. .,ETH Zurich, Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Physical Chemistry (LPC), Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland.
| | - Albena Draycheva
- Max-Planck Institute for Biophysical Chemistry, Department of Physical Biochemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Thomas Bornemann
- Max-Planck Institute for Biophysical Chemistry, Department of Physical Biochemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Wolfgang Wintermeyer
- Max-Planck Institute for Biophysical Chemistry, Department of Physical Biochemistry, Am Fassberg 11, 37077, Göttingen, Germany.
| |
Collapse
|
42
|
Lakomek NA, Draycheva A, Bornemann T, Wintermeyer W. Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201602905] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Nils-Alexander Lakomek
- Department of NMR-based Structural Biology; Max-Planck Institute for Biophysical Chemistry; Am Fassberg 11 37077 Göttingen Germany
- ETH Zurich; Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Physical Chemistry (LPC); Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - Albena Draycheva
- Max-Planck Institute for Biophysical Chemistry; Department of Physical Biochemistry; Am Fassberg 11 37077 Göttingen Germany
| | - Thomas Bornemann
- Max-Planck Institute for Biophysical Chemistry; Department of Physical Biochemistry; Am Fassberg 11 37077 Göttingen Germany
| | - Wolfgang Wintermeyer
- Max-Planck Institute for Biophysical Chemistry; Department of Physical Biochemistry; Am Fassberg 11 37077 Göttingen Germany
| |
Collapse
|
43
|
Zhang H, van Ingen H. Isotope-labeling strategies for solution NMR studies of macromolecular assemblies. Curr Opin Struct Biol 2016; 38:75-82. [PMID: 27295425 DOI: 10.1016/j.sbi.2016.05.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/20/2016] [Accepted: 05/22/2016] [Indexed: 12/21/2022]
Abstract
Proteins come together in macromolecular assemblies, recognizing and binding to each other through their structures, and operating on their substrates through their motions. Detailed characterization of these processes is particularly suited to NMR, a high-resolution technique sensitive to structure, dynamics, and interactions. Advances in isotope-labeling have enabled such studies to an ever-increasing range of systems. Here we highlight recent applications and bring to the fore the range of options to produce labeled proteins and to control the specific placement of isotopes. The increased labeling control and affordability, together with the possibility to combine strategies will further deepen and extend the range of protein assembly investigations.
Collapse
Affiliation(s)
- Heyi Zhang
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden, The Netherlands
| | - Hugo van Ingen
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden, The Netherlands.
| |
Collapse
|
44
|
Vögeli B, Bibow S, Chi CN. Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201511476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Beat Vögeli
- Laboratory of Physical Chemistry; ETH Zurich, ETH-Hönggerberg; CH-8093 Zürich Switzerland
| | - Stefan Bibow
- Laboratory of Physical Chemistry; ETH Zurich, ETH-Hönggerberg; CH-8093 Zürich Switzerland
| | - Celestine N. Chi
- Laboratory of Physical Chemistry; ETH Zurich, ETH-Hönggerberg; CH-8093 Zürich Switzerland
| |
Collapse
|
45
|
Mitrea DM, Cika JA, Guy CS, Ban D, Banerjee PR, Stanley CB, Nourse A, Deniz AA, Kriwacki RW. Nucleophosmin integrates within the nucleolus via multi-modal interactions with proteins displaying R-rich linear motifs and rRNA. eLife 2016; 5:13571. [PMID: 26836305 PMCID: PMC4786410 DOI: 10.7554/elife.13571] [Citation(s) in RCA: 329] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 01/21/2016] [Indexed: 12/21/2022] Open
Abstract
The nucleolus is a membrane-less organelle formed through liquid-liquid phase separation of its components from the surrounding nucleoplasm. Here, we show that nucleophosmin (NPM1) integrates within the nucleolus via a multi-modal mechanism involving multivalent interactions with proteins containing arginine-rich linear motifs (R-motifs) and ribosomal RNA (rRNA). Importantly, these R-motifs are found in canonical nucleolar localization signals. Based on a novel combination of biophysical approaches, we propose a model for the molecular organization within liquid-like droplets formed by the N-terminal domain of NPM1 and R-motif peptides, thus providing insights into the structural organization of the nucleolus. We identify multivalency of acidic tracts and folded nucleic acid binding domains, mediated by N-terminal domain oligomerization, as structural features required for phase separation of NPM1 with other nucleolar components in vitro and for localization within mammalian nucleoli. We propose that one mechanism of nucleolar localization involves phase separation of proteins within the nucleolus. DOI:http://dx.doi.org/10.7554/eLife.13571.001 Inside cells, machines called ribosomes assemble proteins from building blocks known as amino acids. Cells can alter the numbers of ribosomes they produce to match the cell’s demand for new proteins. For instance, when cells grow they require a lot of new proteins and therefore more ribosomes are produced. However, when cells face harsh conditions that cause stress (e.g. exposure to UV radiation or a harmful chemical) they generally stop growing and therefore need fewer ribosomes. In human and other eukaryotic cells, ribosomes are assembled in a structure called the nucleolus. However, because the nucleolus is not separated from the rest of the cell by a membrane, it was not clear how it is able to accumulate large quantities of the proteins and other molecules needed to make ribosomes. Recent work suggests that the nucleolus is formed through a process referred to as “phase separation” in which the liquid in a particular region of the cell has different physical properties to the liquid surrounding it. This is like how oil and water form separate layers when mixed. A protein called nucleophosmin is found at high levels in the nucleolus where it interacts with many other proteins, including those involved in making ribosomes. Nucleophosmin binds to motifs within these proteins that contain multiple copies of an amino acid called arginine (referred to as R-motifs). Now, Mitrea et al. investigate how nucleophosmin binds to R-motif proteins and whether this is important for assembling the nucleolus. A search for R-motifs in a list of over a hundred proteins known to bind to nucleophosmin showed that the majority of these proteins contained multiple R-motifs. Furthermore, when high levels of nucleophosmin and the R-motif proteins were present, they underwent phase separation. Next, Mitrea et al. examine the changes in how nucleophosmin and a ribosomal protein interact before and after phase separation. The experiments show that many molecules of nucleophosmin bind to each other and that multiple regions in nucleophosmin are able to interact with the R-motifs. Together, these interactions produce large assemblies of proteins that result in the creation of separate liquid layers. Furthermore, the experiments show that R-motif proteins and other molecules needed to make ribosomes can be brought together within the same liquid phase by nucleophosmin. Mitrea et al.’s findings provide the first insights into the role of nucleophosmin in the molecular organisation of the nucleolus. The next challenge is to understand how this organisation promotes the production of ribosomes and helps the cell to respond to stressful situations. DOI:http://dx.doi.org/10.7554/eLife.13571.002
Collapse
Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States
| | - Jaclyn A Cika
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States.,Integrative Biomedical Sciences Program, University of Tennessee Health Sciences Center, Memphis, United States
| | - Clifford S Guy
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, United States
| | - David Ban
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States
| | - Priya R Banerjee
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
| | - Christopher B Stanley
- Biology and Biomedical Sciences Group, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, United States
| | - Amanda Nourse
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States.,Molecular Interactions Analysis Shared Resource, St. Jude Children's Research Hospital, Memphis, United States
| | - Ashok A Deniz
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, United States.,Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, United States
| |
Collapse
|
46
|
Vögeli B, Bibow S, Chi CN. Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop. Angew Chem Int Ed Engl 2016; 55:3096-100. [PMID: 26822756 PMCID: PMC4760428 DOI: 10.1002/anie.201511476] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Indexed: 12/14/2022]
Abstract
Allostery has been revealed as an essential property of all proteins. For enzymes, shifting of the structural equilibrium distribution at one site can have substantial impacts on protein dynamics and selectivity. Promising sites of remotely shifting such a distribution by changing the dynamics would be at flexible loops because relatively large changes may be achieved with minimal modification of the protein. A ligand-selective change of binding affinity to the active site of cyclophilin is presented involving tuning of the dynamics of a highly flexible loop. Binding affinity is increased upon substitution of double Gly to Ala at the hinge regions of the loop. Quenching of the motional amplitudes of the loop slightly rearranges the active site. In particular, key residues for binding Phe60 and His126 adopt a more fixed orientation in the bound protein. Our system may serve as a model system for studying the effects of various time scales of loop motion on protein function tuned by mutations.
Collapse
Affiliation(s)
- Beat Vögeli
- Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, CH-8093, Zürich, Switzerland
| | - Stefan Bibow
- Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, CH-8093, Zürich, Switzerland
| | - Celestine N Chi
- Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, CH-8093, Zürich, Switzerland.
| |
Collapse
|
47
|
Ratnayake PU, Prabodha Ekanayaka EA, Komanduru SS, Weliky DP. Full-length trimeric influenza virus hemagglutinin II membrane fusion protein and shorter constructs lacking the fusion peptide or transmembrane domain: Hyperthermostability of the full-length protein and the soluble ectodomain and fusion peptide make significant contributions to fusion of membrane vesicles. Protein Expr Purif 2015; 117:6-16. [PMID: 26297995 DOI: 10.1016/j.pep.2015.08.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Revised: 08/17/2015] [Accepted: 08/18/2015] [Indexed: 10/23/2022]
Abstract
Influenza virus is a class I enveloped virus which is initially endocytosed into a host respiratory epithelial cell. Subsequent reduction of the pH to the 5-6 range triggers a structural change of the viral hemagglutinin II (HA2) protein, fusion of the viral and endosomal membranes, and release of the viral nucleocapsid into the cytoplasm. HA2 contains fusion peptide (FP), soluble ectodomain (SE), transmembrane (TM), and intraviral domains with respective lengths of ∼ 25, ∼ 160, ∼ 25, and ∼ 10 residues. The present work provides a straightforward protocol for producing and purifying mg quantities of full-length HA2 from expression in bacteria. Biophysical and structural comparisons are made between full-length HA2 and shorter constructs including SHA2 ≡ SE, FHA2 ≡ FP+SE, and SHA2-TM ≡ SE+TM constructs. The constructs are helical in detergent at pH 7.4 and the dominant trimer species. The proteins are highly thermostable in decylmaltoside detergent with Tm>90 °C for HA2 with stabilization provided by the SE, FP, and TM domains. The proteins are likely in a trimer-of-hairpins structure, the final protein state during fusion. All constructs induce fusion of negatively-charged vesicles at pH 5.0 with much less fusion at pH 7.4. Attractive protein/vesicle electrostatics play a role in fusion, as the proteins are positively-charged at pH 5.0 and negatively-charged at pH 7.4 and the pH-dependence of fusion is reversed for positively-charged vesicles. Comparison of fusion between constructs supports significant contributions to fusion from the SE and the FP with little effect from the TM.
Collapse
Affiliation(s)
- Punsisi U Ratnayake
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - E A Prabodha Ekanayaka
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - Sweta S Komanduru
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
| |
Collapse
|
48
|
Viral fusion protein transmembrane domain adopts β-strand structure to facilitate membrane topological changes for virus-cell fusion. Proc Natl Acad Sci U S A 2015; 112:10926-31. [PMID: 26283363 DOI: 10.1073/pnas.1501430112] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The C-terminal transmembrane domain (TMD) of viral fusion proteins such as HIV gp41 and influenza hemagglutinin (HA) is traditionally viewed as a passive α-helical anchor of the protein to the virus envelope during its merger with the cell membrane. The conformation, dynamics, and lipid interaction of these fusion protein TMDs have so far eluded high-resolution structure characterization because of their highly hydrophobic nature. Using magic-angle-spinning solid-state NMR spectroscopy, we show that the TMD of the parainfluenza virus 5 (PIV5) fusion protein adopts lipid-dependent conformations and interactions with the membrane and water. In phosphatidylcholine (PC) and phosphatidylglycerol (PG) membranes, the TMD is predominantly α-helical, but in phosphatidylethanolamine (PE) membranes, the TMD changes significantly to the β-strand conformation. Measured order parameters indicate that the strand segments are immobilized and thus oligomerized. (31)P NMR spectra and small-angle X-ray scattering (SAXS) data show that this β-strand-rich conformation converts the PE membrane to a bicontinuous cubic phase, which is rich in negative Gaussian curvature that is characteristic of hemifusion intermediates and fusion pores. (1)H-(31)P 2D correlation spectra and (2)H spectra show that the PE membrane with or without the TMD is much less hydrated than PC and PG membranes, suggesting that the TMD works with the natural dehydration tendency of PE to facilitate membrane merger. These results suggest a new viral-fusion model in which the TMD actively promotes membrane topological changes during fusion using the β-strand as the fusogenic conformation.
Collapse
|
49
|
Abstract
Protein tyrosine kinases differ widely in their propensity to undergo rearrangements
of the N-terminal Asp–Phe–Gly (DFG) motif of the activation
loop, with some, including FGFR1 kinase, appearing refractory to this so-called
‘DFG flip'. Recent inhibitor-bound structures have unexpectedly
revealed FGFR1 for the first time in a ‘DFG-out' state. Here we
use conformationally selective inhibitors as chemical probes for interrogation of
the structural and dynamic features that appear to govern the DFG flip in FGFR1. Our
detailed structural and biophysical insights identify contributions from altered
dynamics in distal elements, including the αH helix, towards the
outstanding stability of the DFG-out complex with the inhibitor ponatinib. We
conclude that the αC-β4 loop and ‘molecular
brake' regions together impose a high energy barrier for this
conformational rearrangement, and that this may have significance for maintaining
autoinhibition in the non-phosphorylated basal state of FGFR1. Receptor tyrosine kinases are key mediators of cell proliferation
that have been implicated in several disease states for which they represent promising
drug targets. Here the authors determine the thermodynamic basis for the low propensity
of FGFR1 to access the DFG-Phe-out conformation required to bind type-II
inhibitors.
Collapse
|
50
|
Roche J, Louis JM, Aniana A, Ghirlando R, Bax A. Complete dissociation of the HIV-1 gp41 ectodomain and membrane proximal regions upon phospholipid binding. JOURNAL OF BIOMOLECULAR NMR 2015; 61:235-48. [PMID: 25631354 PMCID: PMC4398632 DOI: 10.1007/s10858-015-9900-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Accepted: 01/17/2015] [Indexed: 05/22/2023]
Abstract
The envelope glycoprotein gp41 mediates the process of membrane fusion that enables entry of the HIV-1 virus into the host cell. Strong lipid affinity of the ectodomain suggests that its heptad repeat regions play an active role in destabilizing membranes by directly binding to the lipid bilayers and thereby lowering the free-energy barrier for membrane fusion. In such a model, immediately following the shedding of gp120, the N-heptad and C-heptad helices dissociate and melt into the host cell and viral membranes, respectively, pulling the destabilized membranes into juxtaposition, ready for fusion. Post-fusion, reaching the final 6-helix bundle (6 HB) conformation then involves competition between intermolecular interactions needed for formation of the symmetric 6 HB trimer and the membrane affinity of gp41's ectodomain, including its membrane-proximal regions. Our solution NMR study of the structural and dynamic properties of three constructs containing the ectodomain of gp41 with and without its membrane-proximal regions suggests that these segments do not form inter-helical interactions until the very late steps of the fusion process. Interactions between the polar termini of the heptad regions, which are not associating with the lipid surface, therefore may constitute the main driving force initiating formation of the final post-fusion states. The absence of significant intermolecular ectodomain interactions in the presence of dodecyl phosphocholine highlights the importance of trimerization of gp41's transmembrane helix to prevent complete dissociation of the trimer during the course of fusion.
Collapse
Affiliation(s)
- Julien Roche
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 20892, USA
| | | | | | | | | |
Collapse
|