SARS-CoV-2 Structure
Structural Proteins
Structural proteins are the proteins that form the "blueprint" or contribute to the mechanical properties of an organism or microbe.
SARS-CoV-2 is comprised of four structural proteins: (S) Spike protein, (E) Envelope protein, (M) Membrane protein, and (N) Nucleocapsid protein. These four proteins all have major functions and in addition to a lipid membrane produce the identifiable structure and form of the virus.
Structural proteins are the proteins that form the "blueprint" or contribute to the mechanical properties of an organism or microbe.
SARS-CoV-2 is comprised of four structural proteins: (S) Spike protein, (E) Envelope protein, (M) Membrane protein, and (N) Nucleocapsid protein. These four proteins all have major functions and in addition to a lipid membrane produce the identifiable structure and form of the virus.
(S) Spike Protein:
The S proteins present as large protrusions from the surface of the virus. S proteins are responsible for the binding and fusion of the virus to host membranes which allows for entry into host cells. S proteins also assist in promoting adhesion of infected host cells with adjacent non-infected cells to enhance viral spread.
The S proteins present as large protrusions from the surface of the virus. S proteins are responsible for the binding and fusion of the virus to host membranes which allows for entry into host cells. S proteins also assist in promoting adhesion of infected host cells with adjacent non-infected cells to enhance viral spread.
- Virus-host cell receptor binding
(E) Envelope Protein:
The E proteins are tiny proteins in the lipid membrane of the virus. These proteins form structures called viroporins which are essential for viral assembly as well as for release of the virus from host cells.
The E proteins are tiny proteins in the lipid membrane of the virus. These proteins form structures called viroporins which are essential for viral assembly as well as for release of the virus from host cells.
- Virus (virion) assembly
- Viroporin action
(M) Membrane Protein:
M proteins serve in assisting in the bending of the lipid membrane to form a spherical structure encasing the genetic material. Another function of the M protein is also a factor in inhibiting the host immune response by interference with the NFκB (Nuclear Factor Kappa B) pathway.
M proteins serve in assisting in the bending of the lipid membrane to form a spherical structure encasing the genetic material. Another function of the M protein is also a factor in inhibiting the host immune response by interference with the NFκB (Nuclear Factor Kappa B) pathway.
- Virus (virion) assembly
- Immune system interference
(N) Nucleocapsid Protein:
The N protein is the most abundant viral protein and binds to viral RNA to form the core of a ribonucleoprotein which is important in regulating the biological functions of the virus such as gene expression and RNA metabolism. Ribonucleoproteins can also act to suppress a key part of the innate immune system known as RNA silencing.
The N protein is the most abundant viral protein and binds to viral RNA to form the core of a ribonucleoprotein which is important in regulating the biological functions of the virus such as gene expression and RNA metabolism. Ribonucleoproteins can also act to suppress a key part of the innate immune system known as RNA silencing.
- Virus (virion) assembly
- Immune system suppression
A more in-depth overview of the structure of SARS-CoV-2 and its proteins can be found in the article, Structural Proteins in Severe Acute Respiratory Syndrome Coronvavirus-2, Satarker & Nampoothiri (2020)
The SARS-CoV-2 Genome
Coronaviruses have the largest genomes of animal RNA viruses, ranging from 26 - 32 kilobases (kb). This size may be attributable to these viruses' ability to correct errors that are common in genomic replication. This proof-reading ability is not common amongst viruses and helps prevent rapid accumulation of deleterious mutations. Despite this feature, mutations do still arise and can be used to track virus spread and evolution.
SARS-CoV-2 is an enveloped, positive-sense, single-stranded ribonucleic acid virus (ssRNA+) with a genome encoding for about ten genes. Some of these genes encode for polyproteins. Polyproteins are large proteins, that once translated, are divided into multiple smaller proteins. The result is a genome which encodes for an estimated 25-29 different viral proteins in all. Four structural proteins, between five and nine accessory proteins, and sixteen non-structural proteins formed from two polyproteins in the ORF1ab gene.
SARS-CoV-2 Origins & Nucleotide Identity to Other Coronaviruses
|
|
|
|
|
Proudly Presented by