Proteins for Coronavirus Research

Do you have UK, South African, and Brazilian Variant spike protein mutants?

Yes, we offer multiple mutant spike proteins for the SARS-CoV-2 UK, South African, and Brazilian variants as well as many more. There are over 30 spike protein mutants to choose from.

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Do you have an active recombinant SARS-CoV-2 Spike protein?

Yes, we offer SARS-CoV-2 active trimer proteins capable of binding to ACE-2. We also have spike subunits spike RBD proteins, and a chimeric spike-Fc fusion protein. Bulk and custom options are also available.

View our spike proteins

How may I assess the bioactivity of your proteins?

ELISA or SPR binding assays are currently the best option for bioactivity testing of Spike, S1, RBD, and ACE2. Most researchers will be using these proteins in binding assays, as such we have focused our in-house validation on that application. Low nanomolar binding for most of the Spike, S1, RBD in assays with ACE2 is currently regarded as the gold standard.

What is the difference between the full length ectodomain SARS-CoV-2 Spike (Active Trimer) and SARS-CoV-2 Spike (GCN4-IZ)?

The only difference between the two proteins is presence or lack of the GCN4-IZ domain. The full ectodomain in both proteins is the same sequence (Val16-Lys1211), however both Active Trimer and GCN4-IZ Spike proteins contain the endogenous HR1/HR2 trimerization domains. The SARS-CoV-2 Spike (GCN4-IZ) also includes an ectopic GCN4-IZ (Isoleucine Zipper) trimerization domain in addition to the natural HR1/HR2 trimerization motifs  We made versions of Spike protein both with and without this additional GCN4-IZ motif in case the endogenous HR1/HR2 domains were not sufficient to form trimers when these spike proteins were made as recombinant proteins.

The SARS-CoV-2 Active Trimer products made in CHO and HEK293 cells are true trimers when analyzed by Size Exclusion Chromatography (SEC) analysis, demonstrating that the natural HR1/HR2 motifs are sufficient to form Spike trimers.  Addition of the GCN4-IZ domain results in trimeric species and some slightly more oligomerized species in SEC analysis resulting in a more active trimer protein when used as a ligand with ACE2 proteins in ELISAs. 

Why are there mutations in the full-length spike ectodomain proteins?

In the SARS-CoV-2 Spike Protein, the two mutations K986P and V987P are the corresponding mutations to K968P and V969P in the SARS-CoV Spike Protein, which promote the prefusion conformation (Kirchdoerfer et al. 2018). Two additional mutations in the SARS-CoV-2 Spike Protein R682S and R685S eliminate a furin protease cleavage site, making the Spike Protein resistant to furin cleavage.

Do you have an ACE-2 recombinant protein?

Yes, we have several ACE-2 proteins from different species including human, mouse, rat, hamster, and pig. These have been raised in HEK293, CHO, or NS0 host expression systems. We also have biotinylated versions of human ACE-2.

What is the difference in ACE-2 binding affinity of the glycosylated Spike protein and non-glycosylated Spike protein?

Glycosylation of the SAS-CoV-2 Spike RBD protein does not appear to affect its binding affinity to ACE-2. However, it is an important consideration when using these spike proteins as antigen to generate relevant blocking antibodies. In addition, researchers may want to consider glycosylation if using the spike proteins in serological diagnostic assays such as antigen-down ELISAs or lateral flow tests.

Which of the COVID-19 related proteases do you supply?

We have SARS and SARS-CoV-2 virus Papain-like Protease, and the 3CL protease. We also have the related MERS-COV Papain like protease, and its respective 3CL protease.

View Coronavirus Proteases

Read Article: Key Protease Targets for COVID-19

What is the difference between SARS CoV-2 proteins made in different source cells such as HEK293 and CHO?

SARS CoV-2 proteins can be highly glycosylated. When made in eukaryotic cell types such as CHO, HEK293, Sf21, or Tn5, this glycosylation pattern can differ depending on the cell type used. Antibodies made using these proteins might recognize cell type-specific glycan epitopes. In addition, glycans can affect receptor binding interactions, and proteins from a given source cell may work better in your specific assay.

Read Application Note: Glycosylation of the receptor binding domain of COVID-19 virus spike protein.

Can your proteins be used in serological assays and release testing assays?

Yes, we have maximized yields to meet the large mass demands required of serological assays and quality control release testing assays. In addition, we have data over multiple lots that demonstrate consistency in our manufacturing process.

If you would like to easily measure human ACE-2 levels by ELISA, our ACE-2 DuoSet® ELISA kit is designed and validated to deliver you the matched antibody pair, protein controls, and detection reagents you need to quantify natural or recombinant ACE-2. A Quantikine ELISA is also in development.

Please contact us for details on specific products and additional data.

Can you synthesize me a COVID-19 related protein conjugated to my fluorophore of choice?

Yes, we are happy to help with custom conjugation requests. We can either start with one of our existing catalog proteins, or custom synthesize a protein and conjugate it to your desired fluorophore.

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Can you synthesize the pro form of IL-1F7b as a treatment for the COVID-19 hyperinflammatory response?

Yes. We can produce custom research-grade proteins suitable for proof-of-concept studies in vitro and in vivo in animal models. We can also produce GMP-compliant proteins for ex vivo use. Our products are not pharmaceutical grade and are not suitable direct injection into human patients.

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Do you have a reliable and accurate serological assay for COVID-19?

Bio-Techne has partnered with Kantaro Biosciences to develop, scale, manufacture, and distribute an antibody test utilizing the Mount Sinai assay as the underlying technology. Kit production capacity is expected to enable laboratories to conduct in excess of 10 million tests.

This IgG antibody test kit is an enzyme-linked immunosorbent assay or ELISA, designed to measure the presence or absence of anti-SARS-CoV-2 antibodies in addition to measuring the titer (level) of antibodies in a sample. It utilizes two virus antigens, the full-length Spike protein, and its Receptor Binding Domain, which is necessary for viral cell entry and is potentially linked with neutralization. The test kit will use a simple patient blood draw and is designed to be easily run by any laboratory in the world without costly proprietary equipment.