A new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant known as Omicron has caused a rapid increase in recent global patients with coronavirus infectious disease 2019 (COVID-19). To overcome the COVID-19 Omicron variant, production of a recombinant spike receptor binding domain (RBD) is vital for developing a subunit vaccine or a neutralizing antibody. Although bacterial expression has many advantages in the production of recombinant proteins, the spike RBD expressed in a bacterial system experiences a folding problem related to disulfide bond formation. In this study, the soluble Omicron RBD was obtained by a disulfide isomerase-assisted periplasmic expression system in Escherichia coli. The Omicron RBD purified from E. coli was very well recognized by anti-SARS-CoV-2 antibodies, sotrovimab (S309), and CR3022, which were previously reported to bind to various SARS-CoV-2 variants. In addition, the kinetic parameters of the purified Omicron RBD upon binding to the human angiotensin-converting enzyme 2 (ACE2) were similar to those of the Omicron RBD produced in the mammalian expression system. These results suggest that an E. coli expression system would be suitable to produce functional and correctly folded spike RBDs of the next emerging SARS-CoV-2 variants quickly and inexpensively.
Bibliographical noteFunding Information:
W.S.K., J.H.K., S.Y.K., H.D.C. and J.-H.N. were supported by grants from the Basic Science Research Programs (2021R1F1A1060240) and the Bio & Medical Technology Development Programs (2021M3H9A1097596) through the National Research Foundation (NRF) of Korea funded by the Ministry of Science and ICT. J.L., I.J. and S.T.J. were supported by grants from the Bio & Medical Technology Development Programs (2020M3E5E2037775) and the Basic Science Research Programs (2022R1A4A2000827) through the NRF of Korea.
We thank Sangji University Graduate School for supporting scholar grants to Woo Sung Kim and Hee Do Chae.
© 2022 by the authors.
- E. coli
- functional expression
- spike receptor binding domain
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