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#C1200N 3CLPro T21I Expression Kit


Express 3CLpro with the T21I mutation in mammalian cells including HEK293, A549, and many more. Use alongside other 3CLpro mutant proteases and our 3CLglow biosensor assays to test 3CLpro inhibitor efficacy against a panel of mutations in the protease. Available for ordering soon! Reach out to us at with any questions.



3CLpro (Mpro) T21I mutation Expression Kit

T21I is commonly found in the B.1.1.318 variant (Ullrich et al. 2022). Structurally, this mutation resides in the S4' subsite of the 3CLpro enzyme, and it has been shown to have higher catalytic activity compared to the wild-type 3CLpro  in kinetic assays (Duan et al. 2023). Ullrich et al. reported that T21I remained susceptible to nirmatrelvir when using a biochemical FRET assay (Ullrich et al. 2022). However, in a recombinant SARS-CoV-2 assay in huh7-ACE2 cells, T21I exhibits a 4.6-fold IC50 resistance to nirmatrelvir (Iketani et al. 2023). This mutation has been identified in patients and reported to the GISAID database (Shu and McCauley 2017).

  • Identify protease inhibitors that maintain efficacy against the T21I mutation
  • Easy co-expression with our 3CLglow and 3CLglowUp sensors
  • Cost effective screening with minimal safety requirements (BSL-1)

Materials in the Kit:

• 3CLpro T21I in BacMam
• Sodium Butyrate, 500 mM in H2O


Duan, Y., Zhou, H., Liu, X., Iketani, S., Lin, M., Zhang, X., Bian, Q., Wang, H., Sun, H., Hong, S. J., Culbertson, B., Mohri, H., Luck, M. I., Zhu, Y., Liu, X., Lu, Y., Yang, X., Yang, K., Sabo, Y., … Yang, H. (2023). Molecular mechanisms of SARS-COV-2 resistance to Nirmatrelvir. Nature, 622(7982), 376–382.

Iketani, S., Mohri, H., Culbertson, B., Hong, S. J., Duan, Y., Luck, M. I., Annavajhala, M. K., Guo, Y., Sheng, Z., Uhlemann, A.-C., Goff, S. P., Sabo, Y., Yang, H., Chavez, A., & Ho, D. D. (2023). Multiple pathways for SARS-COV-2 resistance to Nirmatrelvir. Nature, 613(7944), 558–564.

Shu, Y., & McCauley, J. (2017). GISAID: Global initiative on sharing all influenza data – from vision to reality. Eurosurveillance, 22(13).

Ullrich, S., Ekanayake, K. B., Otting, G., & Nitsche, C. (2022). Main protease mutants of SARS-COV-2 variants remain susceptible to Nirmatrelvir. Bioorganic & Medicinal Chemistry Letters, 62, 128629.


Additional information


We strive for prompt delivery of each order, so we ship by FedEx 2-day service in lightweight, sturdy, and reusable/biodegradable packaging with an insulated cooler and moisture-resistant refrigerant gel packs. Shipping days are Mon-Wed so product does not sit in transit over the weekend. Web store ships to US & Canada only, contact sales for other locations.

Protocol for Use


Kit Volume

5mL, 30mL

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