Molecular Mechanisms Employed by COVID-19

Over 5 million people worldwide have developed life-threatening infections after contracting COVID-19, the illness caused by the novel severe acute respiratory syndrome SARS-CoV-2 pandemic.

It is necessary to recognize the molecular mechanisms used by SARS-CoV-2 to understand the virus. These molecular mechanisms include the virus’s interaction, entry, and replication within the host cell. The novel SARS-CoV-2 has different proteins being used by the virus at different stages of virus/host cell interaction, host cell entry, and replication.

For instance, the receptor-binding domain (RBD) of its spike protein (S) is used by the virus in order to stick to human cells, as well as for viral entry. The nucleocapsid (N) protein is used by the SARS-CoV-2 virus for viral RNA packaging and translation when it has entered the human cell. As a result, it can be concluded that the spike protein RBD and the N protein are highly immunogenic. This means that both the spike protein RBD and the N protein are effective viral antigens for a number of purposes, from detection and diagnosis of COVID-19, to developing the neutralizing antibodies against them to be used as a safe therapeutic intervention.

2019-nCoV Spike RBD-N Protein Chimera (G19NSD-G242H)

The novel SARS-CoV-2 is an enveloped, positive-sense RNA β-coronavirus virus that is widely distributed in humans and mammals. This particular coronavirus can lead to potentially fatal infections in the human respiratory tract.

SARS-CoV-2 has four key structural proteins. These include:

  • (S) spike glycoprotein
  • (E) Envelope glycoprotein
  • (M) membrane glycoprotein
  • (N) nucleocapsid protein

There are also supporting accessory proteins that are used for replication.

The S protein has two subunits, S1 and S2. The RBD, which is situated on the S1 subunit of the virus, aids in the viral binding to host cell receptor (ACE2) process, as well as facilitating membrane fusion and viral entry. The greater similarity of novel SARS-CoV-2 to human ACE2 has been identified due to a sequence mutation found in the RBD domain. This mutation found in the sequence of the RBD domain leads to antibodies raised against it become specific. This opens up a very promising area to develop tools for diagnosis and antivirals that would work against this particular viral antigen.

In a similar way, SARS-CoV-2’s N protein assembles and encapsulates the RNA genome in the viral membrane. The N protein plays a part in a number of processes, such as:

  • Viral replication
  • Translating viral proteins
  • Packaging new viral genome into new virions

Packaging the new viral genome into these new virions exposes it to the human immune response several times. In addition, it has been found that N protein-specific antibodies produced by the human immune system possess greater sensitivity and longer persistence than the majority of other SARS-CoV-2 structural proteins. It is also easy to detect in the early stages of infection.

Studying and quantifying the N protein can help researchers design reliable biochemical tools for the safe and accurate diagnosis and treatment of COVID-19.

Recombinant protein engineering has given scientists tools to produce these antigens safely in labs with full functionality. Instead of working on two separate antigens, scientists can develop chimera proteins and analyze two different proteins simultaneously.

SignalChem recognizes this need and as a result, has developed a recombinant version of the 2019 novel SARS-CoV-2 Spike RBD-N protein chimera (C19NSD-G242H). The recombinant viral fusion protein was expressed in CHO cells, with the N terminal of Spike S1 RBD (Sequence 319-541) fused to the Nucleocapsid protein (sequence 237-419) protein with a linker HSA (human serum albumin) using a C-terminal His tag. Analysis carried out in-house of the specific binding potential of the RBD-N chimera to the anti-S and anti-N antibodies gave results with far greater affinity when compared to individual S or N protein.

Comparison of SARS-CoV-2 Proteins for Antibody Detection

ELISA plates were coated with recombinant SARS-CoV-2 proteins. HRP-conjugated specific antibodies were added to detect the binding. RBD-N chimera (C19NSD-G242H) protein demonstrated specific binding to anti-S and anti-N antibody with higher affinity comparing to individual S or N protein.

Figure 1. ELISA plates were coated with recombinant SARS-CoV-2 proteins. HRP-conjugated specific antibodies were added to detect the binding. RBD-N chimera (C19NSD-G242H) protein demonstrated specific binding to anti-S and anti-N antibody with higher affinity comparing to individual S or N protein. Image Credit: SignalChem Biotech

SignalChem is a global leader in cell signaling and protein engineering; the company has been carrying out research on the novel coronavirus since the initial outbreak. SignalChem scientists have applied their resources to the understanding of the protein interaction map of SARS-CoV-2 to create active recombinant SARS-CoV-2 and human proteins.

SignalChem is focused on offering other researchers these same central elements that are crucial on drug discovery research projects worldwide. With the support of advanced engineering technology and AI drug development software, projects have already been started by SignalChem, and SignalChem continues to develop expression systems of key COVID-19-related proteins, which includes hot drug targets such as proteases, structural proteins, and non-structural proteins (NSPs).

These catalytically active proteins are fully functional and are ready for use in research projects focusing on the development of drugs to fight SARS-CoV-2 and other coronavirus infections.

About SignalChem Biotech Inc.

SignalChem is a biotech company focused on the research, development, and production of innovative and high-quality human recombinant cell signaling products.

Throughout the years, Signalchem has capitalized on its core expertise in cellular signaling, molecular biology, and protein biochemistry to generate more than 2,000 functional protein products and has established itself as the leader in the industry to produce highly active human recombinant signaling enzymes, especially protein kinases, disease-related mutant kinases, lipid kinases, epigenetic enzymes, ubiquitination-related enzymes, and neurodegenerative disease-related enzymes and proteins.

SignalChem strives to support scientists in academia, pharma and biotech companies around the world by creating effective research tools to advance the basic research in life sciences and to facilitate the efforts in drug discovery and development.


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Last updated: Oct 9, 2020 at 10:52 AM

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