6nb6 | pdb_00006nb6
SARS-CoV complex with human neutralizing S230 antibody Fab fragment (state 1)
Structural highlights
FunctionSPIKE_SARS May down-regulate host tetherin (BST2) by lysosomal degradation, thereby counteracting its antiviral activity.[1] Attaches the virion to the cell membrane by interacting with host receptor, initiating the infection (By similarity). 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 membrane fusion within endosomes.[HAMAP-Rule:MF_04099][2] [3] 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][4] Publication Abstract from PubMedRecent outbreaks of severe acute respiratory syndrome and Middle East respiratory syndrome, along with the threat of a future coronavirus-mediated pandemic, underscore the importance of finding ways to combat these viruses. The trimeric spike transmembrane glycoprotein S mediates entry into host cells and is the major target of neutralizing antibodies. To understand the humoral immune response elicited upon natural infections with coronaviruses, we structurally characterized the SARS-CoV and MERS-CoV S glycoproteins in complex with neutralizing antibodies isolated from human survivors. Although the two antibodies studied blocked attachment to the host cell receptor, only the anti-SARS-CoV S antibody triggered fusogenic conformational changes via receptor functional mimicry. These results provide a structural framework for understanding coronavirus neutralization by human antibodies and shed light on activation of coronavirus membrane fusion, which takes place through a receptor-driven ratcheting mechanism. Unexpected Receptor Functional Mimicry Elucidates Activation of Coronavirus Fusion.,Walls AC, Xiong X, Park YJ, Tortorici MA, Snijder J, Quispe J, Cameroni E, Gopal R, Dai M, Lanzavecchia A, Zambon M, Rey FA, Corti D, Veesler D Cell. 2019 Jan 23. pii: S0092-8674(18)31642-8. doi: 10.1016/j.cell.2018.12.028. PMID:30712865[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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