Characterization of the SARS-CoV-2 S Protein: Biophysical, Biochemical, Structural, and Antigenic Analysis

Natalia G. Herrera, Nicholas C. Morano, Alev Celikgil, George I. Georgiev, Ryan J. Malonis, James H. Lee, Karen Tong, Olivia Vergnolle, Aldo B. Massimi, Laura Y. Yen, Alex J. Noble, Mykhailo Kopylov, Jeffrey B. Bonanno, Sarah C. Garrett-Thomson, David B. Hayes, Robert H. Bortz, Ariel S. Wirchnianski, Catalina Florez, Ethan Laudermilch, Denise HaslwanterJ. Maximilian Fels, M. Eugenia Dieterle, Rohit K. Jangra, Jason Barnhill, Amanda Mengotto, Duncan Kimmel, Johanna P. Daily, Liise Anne Pirofski, Kartik Chandran, Michael Brenowitz, Scott J. Garforth, Edward T. Eng, Jonathan R. Lai, Steven C. Almo

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Coronavirus disease 2019 (COVID-19) is a global health crisis caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and there is a critical need to produce large quantities of high-quality SARS-CoV-2 Spike (S) protein for use in both clinical and basic science settings. To address this need, we have evaluated the expression and purification of two previously reported S protein constructs in Expi293F and ExpiCHO-S cells, two different cell lines selected for increased protein expression. We show that ExpiCHO-S cells produce enhanced yields of both SARS-CoV-2 S proteins. Biochemical, biophysical, and structural (cryo-EM) characterizations of the SARS-CoV-2 S proteins produced in both cell lines demonstrate that the reported purification strategy yields high-quality S protein (nonaggregated, uniform material with appropriate biochemical and biophysical properties), and analysis of 20 deposited S protein cryo-EM structures reveals conformation plasticity in the region composed of amino acids 614-642 and 828-854. Importantly, we show that multiple preparations of these two recombinant S proteins from either cell line exhibit identical behavior in two different serology assays. We also evaluate the specificity of S protein-mediated host cell binding by examining interactions with proposed binding partners in the human secretome and report no novel binding partners and notably fail to validate the Spike:CD147 interaction. In addition, the antigenicity of these proteins is demonstrated by standard ELISAs and in a flexible protein microarray format. Collectively, we establish an array of metrics for ensuring the production of high-quality S protein to support clinical, biological, biochemical, structural, and mechanistic studies to combat the global pandemic caused by SARS-CoV-2.

Original languageEnglish (US)
Pages (from-to)85-102
Number of pages18
JournalACS Omega
Issue number1
StatePublished - Jan 12 2021

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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