SARS-CoV-2 accessory protein 7b forms homotetramers in detergent
Abstract A global pandemic is underway caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 genome, like its predecessor SARS-CoV, contains open reading frames that encode accessory proteins involved in virus-host interactions active during infection and which l...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2022-11-01
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| Series: | Virology Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s12985-022-01920-0 |
| _version_ | 1828096804587044864 |
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| author | Wahyu Surya Maria Queralt-Martin Yuguang Mu Vicente M. Aguilella Jaume Torres |
| author_facet | Wahyu Surya Maria Queralt-Martin Yuguang Mu Vicente M. Aguilella Jaume Torres |
| author_sort | Wahyu Surya |
| collection | DOAJ |
| description | Abstract A global pandemic is underway caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 genome, like its predecessor SARS-CoV, contains open reading frames that encode accessory proteins involved in virus-host interactions active during infection and which likely contribute to pathogenesis. One of these accessory proteins is 7b, with only 44 (SARS-CoV) and 43 (SARS-CoV-2) residues. It has one predicted transmembrane domain fully conserved, which suggests a functional role, whereas most variability is contained in the predicted cytoplasmic C-terminus. In SARS-CoV, 7b protein is expressed in infected cells, and the transmembrane domain was necessary and sufficient for Golgi localization. Also, anti-p7b antibodies have been found in the sera of SARS-CoV convalescent patients. In the present study, we have investigated the hypothesis that SARS-2 7b protein forms oligomers with ion channel activity. We show that in both SARS viruses 7b is almost completely α-helical and has a single transmembrane domain. In SDS, 7b forms various oligomers, from monomers to tetramers, but only monomers when exposed to reductants. Combination of SDS gel electrophoresis and analytical ultracentrifugation (AUC) in both equilibrium and velocity modes suggests a dimer-tetramer equilibrium, but a monomer–dimer–tetramer equilibrium in the presence of reductant. This data suggests that although disulfide-linked dimers may be present, they are not essential to form tetramers. Inclusion of pentamers or higher oligomers in the SARS-2 7b model were detrimental to fit quality. Preliminary models of this association was generated with AlphaFold2, and two alternative models were exposed to a molecular dynamics simulation in presence of a model lipid membrane. However, neither of the two models provided any evident pathway for ions. To confirm this, SARS-2 p7b was studied using Planar Bilayer Electrophysiology. Addition of p7b to model membranes produced occasional membrane permeabilization, but this was not consistent with bona fide ion channels made of a tetrameric assembly of α-helices. |
| first_indexed | 2024-04-11T07:36:21Z |
| format | Article |
| id | doaj.art-537101bc1be440eba70e6a646b1b4159 |
| institution | Directory Open Access Journal |
| issn | 1743-422X |
| language | English |
| last_indexed | 2024-04-11T07:36:21Z |
| publishDate | 2022-11-01 |
| publisher | BMC |
| record_format | Article |
| series | Virology Journal |
| spelling | doaj.art-537101bc1be440eba70e6a646b1b41592022-12-22T04:36:43ZengBMCVirology Journal1743-422X2022-11-0119111210.1186/s12985-022-01920-0SARS-CoV-2 accessory protein 7b forms homotetramers in detergentWahyu Surya0Maria Queralt-Martin1Yuguang Mu2Vicente M. Aguilella3Jaume Torres4School of Biological Sciences, Nanyang Technological UniversityLaboratory of Molecular Biophysics, Department of Physics, Universitat Jaume ISchool of Biological Sciences, Nanyang Technological UniversityLaboratory of Molecular Biophysics, Department of Physics, Universitat Jaume ISchool of Biological Sciences, Nanyang Technological UniversityAbstract A global pandemic is underway caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 genome, like its predecessor SARS-CoV, contains open reading frames that encode accessory proteins involved in virus-host interactions active during infection and which likely contribute to pathogenesis. One of these accessory proteins is 7b, with only 44 (SARS-CoV) and 43 (SARS-CoV-2) residues. It has one predicted transmembrane domain fully conserved, which suggests a functional role, whereas most variability is contained in the predicted cytoplasmic C-terminus. In SARS-CoV, 7b protein is expressed in infected cells, and the transmembrane domain was necessary and sufficient for Golgi localization. Also, anti-p7b antibodies have been found in the sera of SARS-CoV convalescent patients. In the present study, we have investigated the hypothesis that SARS-2 7b protein forms oligomers with ion channel activity. We show that in both SARS viruses 7b is almost completely α-helical and has a single transmembrane domain. In SDS, 7b forms various oligomers, from monomers to tetramers, but only monomers when exposed to reductants. Combination of SDS gel electrophoresis and analytical ultracentrifugation (AUC) in both equilibrium and velocity modes suggests a dimer-tetramer equilibrium, but a monomer–dimer–tetramer equilibrium in the presence of reductant. This data suggests that although disulfide-linked dimers may be present, they are not essential to form tetramers. Inclusion of pentamers or higher oligomers in the SARS-2 7b model were detrimental to fit quality. Preliminary models of this association was generated with AlphaFold2, and two alternative models were exposed to a molecular dynamics simulation in presence of a model lipid membrane. However, neither of the two models provided any evident pathway for ions. To confirm this, SARS-2 p7b was studied using Planar Bilayer Electrophysiology. Addition of p7b to model membranes produced occasional membrane permeabilization, but this was not consistent with bona fide ion channels made of a tetrameric assembly of α-helices.https://doi.org/10.1186/s12985-022-01920-0Accessory protein 7bSARS-CoV-2COVID-19Analytical ultracentrifugationChannel activityCoronavirus |
| spellingShingle | Wahyu Surya Maria Queralt-Martin Yuguang Mu Vicente M. Aguilella Jaume Torres SARS-CoV-2 accessory protein 7b forms homotetramers in detergent Virology Journal Accessory protein 7b SARS-CoV-2 COVID-19 Analytical ultracentrifugation Channel activity Coronavirus |
| title | SARS-CoV-2 accessory protein 7b forms homotetramers in detergent |
| title_full | SARS-CoV-2 accessory protein 7b forms homotetramers in detergent |
| title_fullStr | SARS-CoV-2 accessory protein 7b forms homotetramers in detergent |
| title_full_unstemmed | SARS-CoV-2 accessory protein 7b forms homotetramers in detergent |
| title_short | SARS-CoV-2 accessory protein 7b forms homotetramers in detergent |
| title_sort | sars cov 2 accessory protein 7b forms homotetramers in detergent |
| topic | Accessory protein 7b SARS-CoV-2 COVID-19 Analytical ultracentrifugation Channel activity Coronavirus |
| url | https://doi.org/10.1186/s12985-022-01920-0 |
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