7rbv | pdb_00007rbv
SARS-CoV-2 Spike in complex with PVI.V6-14 Fab
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 PubMedStructural characterization of infection- and vaccination-elicited antibodies in complex with antigen provides insight into the evolutionary arms race between the host and the pathogen and informs rational vaccine immunogen design. We isolated a germ line-encoded monoclonal antibody (mAb) from plasmablasts activated upon mRNA vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and determined its structure in complex with the spike glycoprotein by electron cryomicroscopy (cryo-EM). We show that the mAb engages a previously uncharacterized neutralizing epitope on the spike N-terminal domain (NTD). The high-resolution structure reveals details of the intermolecular interactions and shows that the mAb inserts its heavy complementarity-determining region 3 (HCDR3) loop into a hydrophobic NTD cavity previously shown to bind a heme metabolite, biliverdin. We demonstrate direct competition with biliverdin and that, because of the conserved nature of the epitope, the mAb maintains binding to viral variants B.1.1.7 (alpha), B.1.351 (beta), B.1.617.2 (delta), and B.1.1.529 (omicron). Our study describes a novel conserved epitope on the NTD that is readily targeted by vaccine-induced antibody responses. IMPORTANCE We report the first structure of a vaccine-induced antibody to SARS-CoV-2 spike isolated from plasmablasts 7 days after vaccination. The genetic sequence of the antibody PVI.V6-14 suggests that it is completely unmutated, meaning that this type of B cell did not undergo somatic hypermutation or affinity maturation; this cell was likely already present in the donor and was activated by the vaccine. This is, to our knowledge, also the first structure of an unmutated antibody in complex with its cognate antigen. PVI.V6-14 binds a novel, conserved epitope on the N-terminal domain (NTD) and neutralizes the original viral strain. PVI.V6-14 also binds the newly emerged variants B.1.1.7 (alpha), B.1.351 (beta), B.1.617.2 (delta), and B.1.1.529 (omicron). Given that this antibody was likely already present in the donor prior to vaccination, we believe that this antibody class could potentially "keep up" with the new variants, should they continue to emerge, by undergoing somatic hypermutation and affinity maturation. Structure of a Vaccine-Induced, Germline-Encoded Human Antibody Defines a Neutralizing Epitope on the SARS-CoV-2 Spike N-Terminal Domain.,Altomare CG, Adelsberg DC, Carreno JM, Sapse IA, Amanat F, Ellebedy AH, Simon V, Krammer F, Bajic G mBio. 2022 Jun 28;13(3):e0358021. doi: 10.1128/mbio.03580-21. Epub 2022 Apr 25. PMID:35467422[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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