7f5g
From Proteopedia
The crystal structure of RBD-Nanobody complex, DL4 (SA4)
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 PubMedSARS-CoV-2 engages with human cells through the binding of its Spike receptor-binding domain (S-RBD) to the receptor ACE2. Molecular blocking of this engagement represents a proven strategy to treat COVID-19. Here, we report a single-chain antibody (nanobody, DL4) isolated from immunized alpaca with picomolar affinity to RBD. DL4 neutralizes SARS-CoV-2 pseudoviruses with an IC(50) of 0.101 mug mL(-1) (6.2 nM). A crystal structure of the DL4-RBD complex at 1.75-A resolution unveils the interaction detail and reveals a direct competition mechanism for DL4's ACE2-blocking and hence neutralizing activity. The structural information allows us to rationally design a mutant with higher potency. Our work adds diversity of neutralizing nanobodies against SARS-CoV-2 and should encourage protein engineering to improve antibody affinities in general. Isolation, characterization, and structure-based engineering of a neutralizing nanobody against SARS-CoV-2.,Li T, Zhou B, Li Y, Huang S, Luo Z, Zhou Y, Lai Y, Gautam A, Bourgeau S, Wang S, Bao J, Tan J, Lavillette D, Li D Int J Biol Macromol. 2022 Jun 1;209(Pt A):1379-1388. doi: , 10.1016/j.ijbiomac.2022.04.096. Epub 2022 Apr 20. PMID:35460753[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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