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Recombinant SARS-CoV-2 Spike RBD

COVID-19 Virus Spike RBD, 2019-nCoV S1 RBD, Receptor-Binding Domain, S Protein RBD

Catalog No. Product Name Size List Price (US$) Quantity
BP003052 Recombinant SARS-CoV-2 Spike RBD-His-Avi 100 ug 350.00
BP003052 Recombinant SARS-CoV-2 Spike RBD-His-Avi 1 mg 2200.00

BP003052: Recombinant SARS-CoV-2 Spike RBD-His-Avi

Source: Recombinant SARS-CoV-2 Spike RBD protein (S protein RBD, S1 RBD, Arg319-Asn532) was expressed in mammalian cells with a His tag and Avi at the C-terminus.
Accession: QHD43416.1
Predicted molecular mass: 27 kDa. Due to glycosylation, the recombinant SARS-CoV-2 Spike RBD protein migrates to 36-40 kDa based on the Bis-Tris PAGE result.
Endotoxin: Less than 1 EU per ug by the LAL method.
Formulation: The recombinant SARS-CoV-2 Spike RBD-His-Avi protein was lyophilized from 0.22 um filtered solution in 20 mM PB (pH 7.4). Normally 5% trehalose is added as protectant before lyophilization.
Purity: > 95% by PAGE under reduced condition, and SEC-HPLC.

Shipping: The recombinant SARS-CoV-2 Spike RBD-His-Avi protein is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage:
Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
12 months from date of receipt, -20 to -70°C as supplied.
1 month, 2 to 8°C under sterile conditions after reconstitution.
3 months, -20 to -70°C under sterile conditions after reconstitution.

Questions and answers:

Question: Are the spike protein RBDs between SARS-CoV-2 and SARS-CoV highly conserved? How about their epitope sequences?
Answer: The spike protein RBD from SARS-CoV-2 shows about 74% similarity with the SARS-CoV homologue. Binding test results of SARS-CoV S1 RBD monoclonal antibodies against SARS-CoV-2 spike S1 subunit RBD suggests that difference between the RBD epitope sequences and post-translational modification may play important role in host immune response. It is better to use the SARS-CoV-2 spike S1 subunit or S1 RBD and their specific antibodies in manufacturing of SARS-CoV-2 IgG/IgM antibody test kits and antigen test kits.

Question: Is there false positive result if the spike S1 or S1 RBD-based SARS-CoV-2 IgG/IgM antibody rapid test kit is used for clinical diagnostic test?
Answer: Yes though the possibility is significantly lower than nucleocapsid-based test kit. The cross-reactivity possibility with other coronavirus(es) has to be tested and excluded.

Question: Then why are the nucleocapsid-based SARS-CoV-2 IgG/IgM antibody test kits still widely used?
Answer: The nucleocapsid protein is the most abundant protein in SARS-CoV-2 and is highly immunogenic, it is often used as a marker in diagnostic immunoassays in the ELISA and colloidal gold-based rapid test kits. Its sensitivity is high though crossactivity is also high.

Question: Do you have discount if we place bulk order of the recombinant SARS-CoV-2 (2019-nCoV) spike protein RBD-His-Avi for IVD material?
Answer: Sure. We also sell monoclonal human and rabbit spike RBD antibodies as well as alpaca S1 RBD VHH antibodies as research reagent and IVD materials.

SARS-CoV-2 (2019 nCoV or COVID-19 virus) proteins:

Biotinylated Recombinant SARS-CoV-2 Spike RBD-His-Avi
Recombinant SARS-CoV-2 Spike RBD-His-Avi
Recombinant SARS-CoV-2 Spike RBD-Fc-Avi
Biotinylated Recombinant SARS-CoV-2 Spike S1-His-Avi Protein
Recombinant SARS-CoV-2 Spike S1-His-Avi Protein
Recombinant SARS-CoV-2 Spike S1-Fc-Avi Protein
Recombinant SARS-CoV-2 Spike S-Fc-Avi Protein
Biotinylated Recombinant SARS Spike RBD-His-Avi
Recombinant SARS Spike RBD-His-Avi
Recombinant SARS-CoV-2 Nucleocapsid Protein-His-Avi
Biotinylated Recombinant Human ACE2-His-Avi Protein
Recombinant Human ACE2-His-Avi Protein
Recombinant Human ACE2-Fc-Avi Protein

To check more Syd Labs SARS-CoV-2 (2019-nCoV) Antigen and Antibody Reagents and Discovery Services


The S1 subunit and its receptor binding domain (RBD) of the SARS-CoV-2 (2019-nCoV) spike (S) glycoprotein plays the most important roles in viral attachment, fusion and entry, and serves as a target for development of virus entry inhibitors, neutralizing antibodies, and vaccines. There are two subunits, S1 and S2, in the SARS-CoV-2 spike (S) glycoprotein. The S1 subunit, the N-terminal 14–685 amino acids of the S protein, contains N-terminal domain (NTD), receptor binding domain (RBD, 331-524), and receptor binding motif (RBM). The SARS-CoV and SARS-CoV-2 spike proteins mediate viral entry into host cells by binding to a host receptor, angiotensin-converting enzyme 2 (ACE2), through the receptor-binding domain (RBD), and then fusing the viral and host membranes through the S2 subunit. The ACE2-binding affinity of the Spike RBD of SARS-CoV-2 is 10- to 20-fold higher than that of SARS-CoV.

The SARS-CoV-2 spike RBD has become a popular target of antibodies for diagnostics tests. It is critical to use an active protein with natural conformation and post-translational modification as the antigen, even for the SARS-CoV-2 IgM/IgG test kit (S protein) which is popularly used to check people already carrying immune response against the COVID-19 virus. Thus, the spike RBD should be expressed in mammalian cells, such as HEK 293 and CHO cells.

The amino-acid sequence identity is around 74% between the RBDs in the SARS-CoV and SARS-CoV-2 spike proteins, similar to the 77% identity between the whole spike proteins of SARS-CoV and SARS-CoV-2. Such a high degree of sequence similarity raises the possibility that cross-reactive epitopes may exist. Although the SARS-CoV spike RBD polyclonal antibodies can recognize both viruses, only one out of a few published spike RBD monoclonal antibodies neutralizing SARS-CoV binds to SARS-CoV-2 spike RBD. Out of the 28 residues in the epitope of the spike RBD monoclonal antibody, only 4 residues (86%) in SARS-CoV-2 are different from SARS-CoV. However, the spike RBD mAb binds to SARS-CoV spike RBD (Kd = 1 nM) with a much higher affinity than to SARS-CoV-2 spike RBD (Kd = 115 nM, or 6.3 nM measured by another lab).

Recombinant SARS-CoV-2 spike RBD-Fc and RBD-His proteins are both available with an Avi site, which is for biotinylation. Biotinylated recombinant SARS-CoV-2 spike RBD-His and RBD-Fc proteins are also available. Please ask for a quote if you need SARS-CoV-2 spike protein RBD mutants or a protein with different modification or components.

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