Coding a virus

Below, a covid-19 animation showing the capside
(envelope).

Interestingly, the capside to a virus has to use the same elements repeatedly.
If not, the code would always take more room than the envelope.

From the German-language Wikipedia:

As early as the 1950s, Francis Crick and James Watson assumed that the packaging of the nucleic acid of viruses had to consist of many identical subunits and that these were necessarily arranged symmetrically. ^[1] This results from the consideration that the information on a nucleic acid can never be sufficient to encode a single large protein which completely surrounds this nucleic acid. The coding nucleic acid would arithmetically always take up a larger volume than the protein it encodes. The genetic information must therefore be used several times by many copies of identical proteins.



Coronavirus from Fusion Medical Animation on Vimeo.

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The individual subunits from which a capsomer can in turn be constructed are sometimes referred to as protomers .

With a given genome sequence of a virus, those proteins which form the capsomer can be recognized very easily, since they contain a high concentration of positively charged or basic amino acids ( arginine , lysine , histidine ) in certain sections . These basic protein domains of the capsid proteins (core proteins) are necessary for non- covalent binding to the negatively charged viral nucleic acid which is to be packaged.

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• In the case of non-enveloped viruses, the capsid forms the surface of a virion. As a result, it is directly exposed to attack by the immune system and acts as an antigen . In the case of viruses, the surfaces often change epitope and thereby escape the host's immune system, which is however only possible to a very limited extent in the case of naked capsids, since numerous changes in the capsid proteins can also lead to loss of stability or impairment of self-assembly . Uncovered viruses are therefore generally less variable in surface epitopes than enveloped ones.
• Since regularly arranged proteins are a much stronger antigen than irregularly arranged ones, capsids are particularly suitable as a material for vaccinations . ^[10]
• The capsid of non-enveloped viruses also mediates binding to receptors in the target cell in order to initiate entry into the cell. With some enveloped DNA viruses, a special transport of the capsid to the nuclear pores ensures that the virus genome penetrates into the cell nucleus.
• Due to the ability of capsids to serve as a transport vehicle for nucleic acid in cells , capsids produced in vitro , so-called virus-like particles (VLPs), are of particular interest in genetic engineering and gene therapy .