Cell entry mechanisms of SARS-CoV2. Fusion peptide molecules in the spike protein need to undergo a conformational change ("bending") to help "clip" the 2 membranes together (virus & human cell);energy is needed to overcome a repulsive hydration force. 1/n
pnas.org/content/117/21…
pnas.org/content/117/21…
The fusion process - or final conformational change- varies by availability of multiple cellular proteases, and may be facilitated by environmental factors (physical force/temperature/chemical) in addition to furin preactivation.
2/n
2/n
The SARS-CoV-2 virus is a 'more advanced model' than the original 2003 SARS virus, in that its RBD remains hidden (in lying down / 'off' position) helping it escape our immune surveillance.
While this might theoretically affect its ability to bind to the ACE-2 receptor,
3/6
While this might theoretically affect its ability to bind to the ACE-2 receptor,
3/6
it makes up for this 'hidden' status by greater affinity to the ACE-2 receptor. Thus, in sum, its ACE-2 binding ability is comparable to the 2003 virus. Viruses are known to conceal critical parts of their body by keeping them out of sight in crevices by folding of proteins.
4/6
4/6
Not all parts of the virus are 'attractive' targets for our immune system. In the case of the SARS-CoV-2 virus, the RBD of its spike protein is considered to be one of the most critical immune targets. That is why most vaccines target the spike protein.
5/6
5/6
Although we often hear simplistically about 'virus spike protein binding to our ACE-2 receptor', there are so many processes that influence viral entry. Understanding each one of these physical, chemical& biological elements will help solve many mysteries about the pandemic.
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6/6
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