View source for Sandbox 30005

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{{Theoretical_model}}
== Function ==
'''Surface glycoprotein (S)'''
The lungs are the organs most affected by COVID-19 because the virus accesses host cells via the enzyme angiotensin-converting enzyme 2 (ACE2), which is most abundant in the type II alveolar cells of the lungs. The virus uses a special surface glycoprotein called a "spike" (peplomer) to connect to ACE2 and enter the host cell.[http://en.wikipedia.org/wiki/Coronavirus_disease_2019 (Wikipedia)].

<snapshot name='84/842076/State_1/1'>Complex Spine S protein and ACE2</snapshot>

<snapshot name='84/842076/No_d/1'>Spine S protein</snapshot>


Spike protein S1 (residue 14-685): attaches the virion to the cell membrane by interacting with host receptor, initiating the infection. Binding to human ACE2 and CLEC4M/DC-SIGNR receptors and internalization of the virus into the endosomes of the host cell induces conformational changes in the S glycoprotein. Proteolysis by cathepsin CTSL may unmask the fusion peptide of S2 and activate membranes fusion within endosomes.
Spike protein S2 (residue 686-1273): mediates fusion of the virion and cellular membranes by acting as a class I viral fusion protein. Under the current model, the protein has at least three conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes.
Spike protein S2' (residue 816-1273): acts as a viral fusion peptide which is unmasked following S2 cleavage occurring upon virus endocytosis.<ref>[http://zhanglab.ccmb.med.umich.edu/COVID-19/ Modeling of the SARS-COV-2 Genome]</ref><ref>pmid 32200634</ref>

== Disease ==

== Relevance ==

== Structural highlights ==

== See also ==
[[Coronavirus_Disease 2019 (COVID-19)]]
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== References ==
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