Structure of SARS-CoV-2 M protein in lipid nanodiscs
- University of California, Berkeley, United States
- University of Chicago, United States
- Thermo Fisher Scientific, Netherlands
Abstract
SARS-CoV-2 encodes four structural proteins incorporated into virions, spike (S), envelope (E), nucleocapsid (N), and membrane (M). M plays an essential role in viral assembly by organizing other structural proteins through physical interactions and directing them to sites of viral budding. As the most abundant protein in the viral envelope and a target of patient antibodies, M is a compelling target for vaccines and therapeutics. Still, the structure of M and molecular basis for its role in virion formation are unknown. Here, we present the cryo-EM structure of SARS-CoV-2 M in lipid nanodiscs to 3.5 Å resolution. M forms a 50 kDa homodimer that is structurally related to the SARS-CoV-2 ORF3a viroporin, suggesting a shared ancestral origin. Structural comparisons reveal how intersubunit gaps create a small, enclosed pocket in M and large open cavity in ORF3a, consistent with a structural role and ion channel activity, respectively. M displays a strikingly electropositive cytosolic surface that may be important for interactions with N, S, and viral RNA. Molecular dynamics simulations show a high degree of structural rigidity in a simple lipid bilayer and support a role for M homodimers in scaffolding viral assembly. Together, these results provide insight into roles for M in coronavirus assembly and structure.
Data availability
All data and reagents associated with this study are publicly available. The final model is in the PDB under 8CTK, the final map is in the EMDB under EMD-26993, and micrographs (original and motion corrected) and final particle stack are deposited in EMPIAR under 11067.
Article and author information
Author details
Funding
New York Stem Cell Foundation (R-N145)
- Stephen G Brohawn
Fast Grants
- Stephen G Brohawn
National Science Foundation
- Kimberly A Dolan
National Science Foundation (CHE-2029092)
- Mandira Dutta
- Gregory A Voth
National Science Foundation (OAC-1818253)
- Gregory A Voth
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2022, Dolan et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Structure of SARS-CoV-2 M protein in lipid nanodiscs
eLife 11:e81702.
https://doi.org/10.7554/eLife.81702
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