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Medeiros-Silva J, Dregni AJ, Somberg NH, Duan P, Hong M. Atomic structure of the open SARS-CoV-2 E viroporin. Sci Adv 2023; 9:eadi9007. [PMID: 37831764 PMCID: PMC10575589 DOI: 10.1126/sciadv.adi9007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/08/2023] [Indexed: 10/15/2023]
Abstract
The envelope (E) protein of the SARS-CoV-2 virus forms cation-conducting channels in the endoplasmic reticulum Golgi intermediate compartment (ERGIC) of infected cells. The calcium channel activity of E is associated with the inflammatory responses of COVID-19. Using solid-state NMR (ssNMR) spectroscopy, we have determined the open-state structure of E's transmembrane domain (ETM) in lipid bilayers. Compared to the closed state, open ETM has an expansive water-filled amino-terminal chamber capped by key glutamate and threonine residues, a loose phenylalanine aromatic belt in the middle, and a constricted polar carboxyl-terminal pore filled with an arginine and a threonine residue. This structure gives insights into how protons and calcium ions are selected by ETM and how they permeate across the hydrophobic gate of this viroporin.
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Affiliation(s)
| | - Aurelio J. Dregni
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Pu Duan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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2
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Somberg NH, Medeiros‐Silva J, Jo H, Wang J, DeGrado WF, Hong M. Hexamethylene amiloride binds the SARS-CoV-2 envelope protein at the protein-lipid interface. Protein Sci 2023; 32:e4755. [PMID: 37632140 PMCID: PMC10503410 DOI: 10.1002/pro.4755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/09/2023] [Accepted: 08/11/2023] [Indexed: 08/27/2023]
Abstract
The SARS-CoV-2 envelope (E) protein forms a five-helix bundle in lipid bilayers whose cation-conducting activity is associated with the inflammatory response and respiratory distress symptoms of COVID-19. E channel activity is inhibited by the drug 5-(N,N-hexamethylene) amiloride (HMA). However, the binding site of HMA in E has not been determined. Here we use solid-state NMR to measure distances between HMA and the E transmembrane domain (ETM) in lipid bilayers. 13 C, 15 N-labeled HMA is combined with fluorinated or 13 C-labeled ETM. Conversely, fluorinated HMA is combined with 13 C, 15 N-labeled ETM. These orthogonal isotopic labeling patterns allow us to conduct dipolar recoupling NMR experiments to determine the HMA binding stoichiometry to ETM as well as HMA-protein distances. We find that HMA binds ETM with a stoichiometry of one drug per pentamer. Unexpectedly, the bound HMA is not centrally located within the channel pore, but lies on the lipid-facing surface in the middle of the TM domain. This result suggests that HMA may inhibit the E channel activity by interfering with the gating function of an aromatic network. These distance data are obtained under much lower drug concentrations than in previous chemical shift perturbation data, which showed the largest perturbation for N-terminal residues. This difference suggests that HMA has higher affinity for the protein-lipid interface than the channel pore. These results give insight into the inhibition mechanism of HMA for SARS-CoV-2 E.
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Affiliation(s)
- Noah H. Somberg
- Department of ChemistryMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - João Medeiros‐Silva
- Department of ChemistryMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
| | - Hyunil Jo
- Department of Pharmaceutical ChemistryUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | - Jun Wang
- Department of Medicinal Chemistry, Ernest Mario School of Pharmacy, Rutgersthe State University of New JerseyPiscatawayNew JerseyUSA
| | - William F. DeGrado
- Department of Pharmaceutical ChemistryUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | - Mei Hong
- Department of ChemistryMassachusetts Institute of TechnologyCambridgeMassachusettsUSA
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3
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Kratochvil HT, Watkins LC, Mravic M, Thomaston JL, Nicoludis JM, Somberg NH, Liu L, Hong M, Voth GA, DeGrado WF. Transient water wires mediate selective proton transport in designed channel proteins. Nat Chem 2023; 15:1012-1021. [PMID: 37308712 PMCID: PMC10475958 DOI: 10.1038/s41557-023-01210-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 04/19/2023] [Indexed: 06/14/2023]
Abstract
Selective proton transport through proteins is essential for forming and using proton gradients in cells. Protons are conducted along hydrogen-bonded 'wires' of water molecules and polar side chains, which, somewhat surprisingly, are often interrupted by dry apolar stretches in the conduction pathways, inferred from static protein structures. Here we hypothesize that protons are conducted through such dry spots by forming transient water wires, often highly correlated with the presence of the excess protons in the water wire. To test this hypothesis, we performed molecular dynamics simulations to design transmembrane channels with stable water pockets interspersed by apolar segments capable of forming flickering water wires. The minimalist designed channels conduct protons at rates similar to viral proton channels, and they are at least 106-fold more selective for H+ over Na+. These studies inform the mechanisms of biological proton conduction and the principles for engineering proton-conductive materials.
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Affiliation(s)
- Huong T Kratochvil
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, USA.
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Laura C Watkins
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics and James Franck Institute, The University of Chicago, Chicago, IL, USA
- Kemper Insurance, Chicago, IL, USA
| | - Marco Mravic
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, USA
- Department of Integrative Structural and Computational Biology Scripps Research Institute, La Jolla, CA, USA
| | - Jessica L Thomaston
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, USA
| | - John M Nicoludis
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, USA
- Genentech, San Francisco, CA, USA
| | - Noah H Somberg
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics and James Franck Institute, The University of Chicago, Chicago, IL, USA.
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, USA.
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Somberg NH, Wu WW, Medeiros-Silva J, Dregni AJ, Jo H, DeGrado WF, Hong M. SARS-CoV-2 Envelope Protein Forms Clustered Pentamers in Lipid Bilayers. Biochemistry 2022; 61:2280-2294. [PMID: 36219675 PMCID: PMC9583936 DOI: 10.1021/acs.biochem.2c00464] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/26/2022] [Indexed: 11/30/2022]
Abstract
The SARS-CoV-2 envelope (E) protein is a viroporin associated with the acute respiratory symptoms of COVID-19. E forms cation-selective ion channels that assemble in the lipid membrane of the endoplasmic reticulum Golgi intermediate compartment. The channel activity of E is linked to the inflammatory response of the host cell to the virus. Like many viroporins, E is thought to oligomerize with a well-defined stoichiometry. However, attempts to determine the E stoichiometry have led to inconclusive results and suggested mixtures of oligomers whose exact nature might vary with the detergent used. Here, we employ 19F solid-state nuclear magnetic resonance and the centerband-only detection of exchange (CODEX) technique to determine the oligomeric number of E's transmembrane domain (ETM) in lipid bilayers. The CODEX equilibrium value, which corresponds to the inverse of the oligomeric number, indicates that ETM assembles into pentamers in lipid bilayers, without any detectable fraction of low-molecular-weight oligomers. Unexpectedly, at high peptide concentrations and in the presence of the lipid phosphatidylinositol, the CODEX data indicate that more than five 19F spins are within a detectable distance of about 2 nm, suggesting that the ETM pentamers cluster in the lipid bilayer. Monte Carlo simulations that take into account peptide-peptide and peptide-lipid interactions yielded pentamer clusters that reproduced the CODEX data. This supramolecular organization is likely important for E-mediated virus assembly and budding and for the channel function of the protein.
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Affiliation(s)
- Noah H. Somberg
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Westley W. Wu
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Aurelio J. Dregni
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Hyunil Jo
- Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, University of California, San Francisco, San Francisco, CA 94158
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, University of California, San Francisco, San Francisco, CA 94158
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
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Dolnik M, Konow C, Somberg NH, Epstein IR. Effect of obstructions on growing Turing patterns. Chaos 2022; 32:073127. [PMID: 35907715 DOI: 10.1063/5.0099753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
We study how Turing pattern formation on a growing domain is affected by discrete domain discontinuities. We use the Lengyel-Epstein reaction-diffusion model to numerically simulate Turing pattern formation on radially expanding circular domains containing a variety of obstruction geometries, including obstructions spanning the length of the domain, such as walls and slits, and local obstructions, such as small blocks. The pattern formation is significantly affected by the obstructions, leading to novel pattern morphologies. We show that obstructions can induce growth mode switching and disrupt local pattern formation and that these effects depend on the shape and placement of the objects as well as the domain growth rate. This work provides a customizable framework to perform numerical simulations on different types of obstructions and other heterogeneous domains, which may guide future numerical and experimental studies. These results may also provide new insights into biological pattern growth and formation, especially in non-idealized domains containing noise or discontinuities.
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Affiliation(s)
- Milos Dolnik
- Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Christopher Konow
- Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Noah H Somberg
- Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Irving R Epstein
- Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02453, USA
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Medeiros-Silva J, Somberg NH, Wang HK, McKay MJ, Mandala VS, Dregni AJ, Hong M. pH- and Calcium-Dependent Aromatic Network in the SARS-CoV-2 Envelope Protein. J Am Chem Soc 2022; 144:6839-6850. [PMID: 35380805 DOI: 10.1021/jacs.2c00973] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The envelope (E) protein of the SARS-CoV-2 virus is a membrane-bound viroporin that conducts cations across the endoplasmic reticulum Golgi intermediate compartment (ERGIC) membrane of the host cell to cause virus pathogenicity. The structure of the closed state of the E transmembrane (TM) domain, ETM, was recently determined using solid-state NMR spectroscopy. However, how the channel pore opens to mediate cation transport is unclear. Here, we use 13C and 19F solid-state NMR spectroscopy to investigate the conformation and dynamics of ETM at acidic pH and in the presence of calcium ions, which mimic the ERGIC and lysosomal environment experienced by the E protein in the cell. Acidic pH and calcium ions increased the conformational disorder of the N- and C-terminal residues and also increased the water accessibility of the protein, indicating that the pore lumen has become more spacious. ETM contains three regularly spaced phenylalanine (Phe) residues in the center of the peptide. 19F NMR spectra of para-fluorinated Phe20 and Phe26 indicate that both residues exhibit two sidechain conformations, which coexist within each channel. These two Phe conformations differ in their water accessibility, lipid contact, and dynamics. Channel opening by acidic pH and Ca2+ increases the population of the dynamic lipid-facing conformation. These results suggest an intricate aromatic network that regulates the opening of the ETM channel pore. This aromatic network may be a target for E inhibitors against SARS-CoV-2 and related coronaviruses.
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Affiliation(s)
- João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Noah H Somberg
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Harrison K Wang
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Matthew J McKay
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Venkata S Mandala
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Aurelio J Dregni
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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Somberg NH, Gelenter MD, Hong M. Comparative analysis of 13C chemical shifts of β-sheet amyloid proteins and outer membrane proteins. J Biomol NMR 2021; 75:151-166. [PMID: 33844106 PMCID: PMC8828358 DOI: 10.1007/s10858-021-00364-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/24/2021] [Indexed: 05/19/2023]
Abstract
Cross-β amyloid fibrils and membrane-bound β-barrels are two important classes of β-sheet proteins. To investigate whether there are systematic differences in the backbone and sidechain conformations of these two families of proteins, here we analyze the 13C chemical shifts of 17 amyloid proteins and 7 β-barrel membrane proteins whose high-resolution structures have been determined by NMR. These 24 proteins contain 373 β-sheet residues in amyloid fibrils and 521 β-sheet residues in β-barrel membrane proteins. The 13C chemical shifts are shown in 2D 13C-13C correlation maps, and the amino acid residues are categorized by two criteria: (1) whether they occur in β-strand segments or in loops and turns; (2) whether they are water-exposed or dry, facing other residues or lipids. We also examine the abundance of each amino acid in amyloid proteins and β-barrels and compare the sidechain rotameric populations. The 13C chemical shifts indicate that hydrophobic methyl-rich residues and aromatic residues exhibit larger static sidechain conformational disorder in amyloid fibrils than in β-barrels. In comparison, hydroxyl- and amide-containing polar residues have more ordered sidechains and more ordered backbones in amyloid fibrils than in β-barrels. These trends can be explained by steric zipper interactions between β-sheet planes in cross-β fibrils, and by the interactions of β-barrel residues with lipid and water in the membrane. These conformational trends should be useful for structural analysis of amyloid fibrils and β-barrels based principally on NMR chemical shifts.
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Affiliation(s)
- Noah H Somberg
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA
| | - Martin D Gelenter
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA.
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Konow C, Somberg NH, Chavez J, Epstein IR, Dolnik M. Turing patterns on radially growing domains: experiments and simulations. Phys Chem Chem Phys 2019; 21:6718-6724. [PMID: 30860212 DOI: 10.1039/c8cp07797e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We study Turing pattern formation in a system undergoing radial growth in two dimensions. The photosensitive chlorine dioxide-iodine-malonic acid reaction is illuminated to inhibit patterning, with a growing non-illuminated circular domain in which the pattern develops. We examine the relationship between the linear radial growth rate and the resulting pattern morphology. Faster growth causes the pattern to form parallel to the growing boundary as concentric rings, while slower growth leads to pattern formation perpendicular to the growing boundary. We observe three distinct growth modes for the Turing patterns, which also depend on the radial growth rate. The experimental results are qualitatively reproduced in numerical simulations using the Lengyel-Epstein model with an additional term to account for the photosensitivity of the reaction. These results may provide new insight into how patterns form in growing biological systems.
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Affiliation(s)
- Christopher Konow
- Department of Chemistry, Brandeis University, MS 015, Waltham, MA 02454, USA.
| | - Noah H Somberg
- Department of Chemistry, Brandeis University, MS 015, Waltham, MA 02454, USA.
| | - Jocelyne Chavez
- Department of Chemistry and Biochemistry, New Mexico State University, MSC 3C, P.O. Box 30001, Las Cruces, NM 88003-8001, USA
| | - Irving R Epstein
- Department of Chemistry, Brandeis University, MS 015, Waltham, MA 02454, USA.
| | - Milos Dolnik
- Department of Chemistry, Brandeis University, MS 015, Waltham, MA 02454, USA.
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