Looking at electron-microscopic images of the virus, it appears they are of different size. Also, the S protein-gen occurs only once in the genome. In the final virus, the number of spikes seems to depend on the size of the virus. The density of spikes appears fairly constant between different sizes of the virus, again from looking at the images.
Could it be that the virus assembly starts with grabbing a random vacuole (with human cell membrane) and then somehow repeat-build Spikes (S), held at a distance from each other by M or N proteins in between, until the vacuole membrane is filled with Spikes?
Robert ten Hoor. [email protected]
Please I am interested in this aspect and I hope to join the group and wish all health and success
Hi Robert Hoor,
As the spike protein is trimeric in nature and directly attached to the outer membrane along with some corresponding glycoproteins. Now, the questionable points I think which you want to question here is: Generally what happens when it binds to the ACE-2 Receptor? and how does the positive sense single stranded RNA of the virus gets translocated into the cell?
Answer is that, the spike protein has S1 and S2 subunit accommodated with during cleavage site between them. S1 subunit of S protein binds to the ACE-2 receptor and other side some portion of the S2 sub unit gets cleaved by Furin/ cathepsine-L/ TMPRRS2 enzymatic factors, this is called as Prefusion state. Now, the detached polypeptide portion of S-protein gets stretched by itself (open state) and connects to the cell membrane and again corresponding folds back to the virus outer membrane (Extension state) and creates a connecting bridge which helps in the Viral ssRNA and alternatively introduced ssRNA is garnered into the endosome of cell. The Nucleoprotein gets unfolded and Positive sense viral RNA directly works similar to the m-RNA and about on two ORFs (Open Reading Frames- PP1a and PP1ab) gets translated to code about on 27 non structural proteins. The non structural protein 1(nsp1) then blocks the ribosomal functioning and some of other nsp forms RNA Polymerase enzyme for the construction of subgenomic positive sense RNAs. Then these subgenomic RNAs which are having the ORFs of structural protein including M and S (spike protein ORF) goes through the translation process and makes spike prorteins and others as well. When these structural proteins gets translated then the replicated viral ss-RNA gets covered by the structural proteins and such appropriate packing is done by the golgi complex of infected cell. That's how such virions are formed along with the outer covering of spike proteins and glycoproteins.
(There are other aspects of it as well like replication/transcription of virus in RTCs which I haven't discussed here, as the answer would go very long)
Thank you.
Thank you very much, but unfortunately this appears to be the answer to a different question... (which is stated at the beginning)
