View source for 6xm3


==Structure of SARS-CoV-2 spike at pH 5.5, single RBD up, conformation 1==
<StructureSection load='6xm3' size='340' side='right'caption='[[6xm3]], [[Resolution|resolution]] 2.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6xm3]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/2019-ncov 2019-ncov]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6XM3 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6XM3 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat"><div style='overflow: auto; max-height: 3em;'>[[6xlu|6xlu]], [[6xm0|6xm0]]</div></td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">S, 2 ([https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=2697049 2019-nCoV])</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=6xm3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6xm3 OCA], [https://pdbe.org/6xm3 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6xm3 RCSB], [https://www.ebi.ac.uk/pdbsum/6xm3 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6xm3 ProSAT]</span></td></tr>
</table>
== Function ==
[[https://www.uniprot.org/uniprot/SPIKE_SARS2 SPIKE_SARS2]] attaches the virion to the cell membrane by interacting with host receptor, initiating the infection (By similarity). Binding to human ACE2 receptor and internalization of the virus into the endosomes of the host cell induces conformational changes in the Spike glycoprotein (PubMed:32142651, PubMed:32075877, PubMed:32155444). Uses also human TMPRSS2 for priming in human lung cells which is an essential step for viral entry (PubMed:32142651). Proteolysis by cathepsin CTSL may unmask the fusion peptide of S2 and activate membranes fusion within endosomes.[HAMAP-Rule:MF_04099]<ref>PMID:32075877</ref> <ref>PMID:32142651</ref> <ref>PMID:32155444</ref>   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.[HAMAP-Rule:MF_04099]  Acts as a viral fusion peptide which is unmasked following S2 cleavage occurring upon virus endocytosis.[HAMAP-Rule:MF_04099] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The SARS-CoV-2 spike employs mobile receptor-binding domains (RBDs) to engage the human ACE2 receptor and to facilitate virus entry, which can occur through low-pH-endosomal pathways. To understand how ACE2 binding and low pH affect spike conformation, we determined cryo-electron microscopy structures-at serological and endosomal pH-delineating spike recognition of up to three ACE2 molecules. RBDs freely adopted "up" conformations required for ACE2 interaction, primarily through RBD movement combined with smaller alterations in neighboring domains. In the absence of ACE2, single-RBD-up conformations dominated at pH 5.5, resolving into a solitary all-down conformation at lower pH. Notably, a pH-dependent refolding region (residues 824-858) at the spike-interdomain interface displayed dramatic structural rearrangements and mediated RBD positioning through coordinated movements of the entire trimer apex. These structures provide a foundation for understanding prefusion-spike mechanics governing endosomal entry; we suggest that the low pH all-down conformation potentially facilitates immune evasion from RBD-up binding antibody.

Cryo-EM Structures of SARS-CoV-2 Spike without and with ACE2 Reveal a pH-Dependent Switch to Mediate Endosomal Positioning of Receptor-Binding Domains.,Zhou T, Tsybovsky Y, Gorman J, Rapp M, Cerutti G, Chuang GY, Katsamba PS, Sampson JM, Schon A, Bimela J, Boyington JC, Nazzari A, Olia AS, Shi W, Sastry M, Stephens T, Stuckey J, Teng IT, Wang P, Wang S, Zhang B, Friesner RA, Ho DD, Mascola JR, Shapiro L, Kwong PD Cell Host Microbe. 2020 Dec 9;28(6):867-879.e5. doi: 10.1016/j.chom.2020.11.004. , Epub 2020 Nov 17. PMID:33271067<ref>PMID:33271067</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6xm3" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: 2019-ncov]]
[[Category: Large Structures]]
[[Category: Kwong, P D]]
[[Category: Olia, A]]
[[Category: Tsybovsky, Y]]
[[Category: Zhou, T]]
[[Category: Covid19]]
[[Category: Sars-cov-2 spike]]
[[Category: Viral protein]]