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Cryo-EM structure of the Omicron S in complex with 35B5 Fab(1 down-, 1 up- and 1 invisible RBDs)
Structural highlights
FunctionSPIKE_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][1] [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] Publication Abstract from PubMedThe SARS-CoV-2 Omicron variant harbors more than 30 mutations in the spike protein, leading to immune evasion from many therapeutic neutralizing antibodies. We reveal that a receptor-binding domain (RBD)-targeting monoclonal antibody, 35B5, exhibits potent neutralizing efficacy to Omicron. Cryo-electron microscopy structures of the extracellular domain trimer of Omicron spike with 35B5 Fab reveal that Omicron spike exhibits tight trimeric packing and high thermostability, as well as significant antigenic shifts and structural changes, within the RBD, N-terminal domain (NTD), and subdomains 1 and 2. However, these changes do not affect targeting of the invariant 35B5 epitope. 35B5 potently neutralizes SARS-CoV-2 Omicron and other variants by causing significant conformational changes within a conserved N-glycan switch that controls the transition of RBD from the "down" state to the "up" state, which allows recognition of the host entry receptor ACE2. This mode of action and potent neutralizing capacity of 35B5 indicate its potential therapeutic application for SARS-CoV-2. 35B5 antibody potently neutralizes SARS-CoV-2 Omicron by disrupting the N-glycan switch via a conserved spike epitope.,Wang X, Chen X, Tan J, Yue S, Zhou R, Xu Y, Lin Y, Yang Y, Zhou Y, Deng K, Chen Z, Ye L, Zhu Y Cell Host Microbe. 2022 Jun 8;30(6):887-895.e4. doi: 10.1016/j.chom.2022.03.035. , Epub 2022 Mar 29. PMID:35436443[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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