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According to several sources, Coronavirus is a helical virus, i.e. it should have a helical capsid. Although most sources did not labelled or pointed any kind of capsid. It was mysterious to watch diagrams of spherical envelops with no underneath capsids.

enter image description here Cutaway view of coronavirus from Wikipedia

David Goodsell painting on PDB
enter image description here No mention of capsid.

Initially I guessed the proteins around the RNA fibre formed the capsid, not labelled otherwise. Alternatively I was speculating whether coronavirus is lacking the capsid.

However a researchgate paper picture (heavily diagrammatic) shows a polygonal capsid, the picture is captioned as coronavirus. screenshot from researchgate

It makes me think of whether the capsid is like a hollow spherical or polygonal thing spirally wrapped.

Now my questions are .

  1. What is the actual/ realistic shape of coronavirus capsid?

  2. Does it really contain a capsid?

  3. (Just speculating) Is it SARS-CoV2 lacking a capsid, and thus special exception from g eneral description of coronavirus?

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    $\begingroup$ Just to clarify - are you asking about coronaviruses in general, or about SARS-CoV-2 specifically? $\endgroup$
    – John Dvorak
    Apr 15, 2020 at 12:46
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    $\begingroup$ Yes I am asking about Coronavirus in general but is Sars cov2 an exception? $\endgroup$
    – Always Confused
    Apr 15, 2020 at 12:49
  • $\begingroup$ "helical" does not mean "spherical". Who says coronaviruses are "helical" (esp. their capsids)? $\endgroup$
    – Fizz
    Jan 5, 2021 at 3:35

1 Answer 1

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Does it really contain a capsid?

Yes. Coronaviruses have a capsid, but it's not reminiscent of the polygonal (icosahedral) capsid depicted in the Research Gate picture you referenced. Icosahedral capsids form a sort of shell around the viral genome, where helical capsids actually bind the viral nucleic acids, holding them in a more rigid shape.

Is it SARS-CoV2 lacking a capsid, and thus special exception from general description of coronavirus?

SARS-CoV-2 is not an exception. In fact, its nucleocapsid is a target for diagnostic tests.

What is the actual/ realistic shape of coronavirus capsid?

It is actually depicted in Goodsell animation you referenced. The nucleocapsid proteins are the squigly bits in and around the genomic RNA (labeled "N", for Nucleocapsid). The actual capsid is the complete complex of N proteins bound to genomic RNA, so it doesn't have that polygonal outline that maybe we're used to when we see depictions of viruses. If you want a more detailed look at the actual capsid protein structure, there's a depiction of its crystal structure in this New York Times piece co-authored by Carl Zimmer.

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