![]() ![]() The spike protein (S protein) of SARS-CoV has pivotal roles in viral infection and pathogenesis. The cell entry programs for these viruses are orchestrated by the viral spike (S) proteins that bind cellular receptors and also mediate virus-cell membrane fusions. After entering into respiratory or gastrointestinal tracts, these viruses establish themselves by entering and infecting lumenal macrophages and epithelial cells. The CoVs are widely distributed in nature and their zoonotic transmissions into human populations can cause epidemic disease. The functional role of MHV and SARS-CoV HR was confirmed by mutating key residues and by inhibition experiments using HR2 peptides. For SARS-CoV and MHV, the post-fusion structures of the HR have been solved they form the characteristic six-helix bundle. Heptad repeats comprise a repetitive heptapeptide abcdefg with a and d being hydrophobic residues characteristic of the formation of coiled-coil that participate in the fusion process. Both are able to function as receptor binding domains (RBDs) and bind variety of proteins and sugars.Ĭoronavirus spike proteins contain two heptad repeats in their S2 domain, a feature typical of a class I viral fusion proteins. The S1 contains two subdomains, a N-terminal domain (NTD) and a C-terminal domain (CTD). The S2 subunit is the most conserved region of the protein, whereas the S1 subunit diverges in sequence even among species of a single coronavirus (Figure 2). The formation of an α-helical coiled-coil structure is characteristic of this class of fusion protein, which contain in their C-terminal part regions predicted to have an α-helical secondary structure and to form coiled-coils. ![]() The coronavirus spike protein is a class I fusion protein. This has important consequences on their fusogenicity. Interestingly, within the betacoronavirus mouse hepatitis virus (MHV) species, different strains, such as MHV-2 and MHV-A59 display different cleavage requirements. With some exceptions, in most alphacoronaviruses and the betacoronavirus SARS-CoV, the virions harbor a spike protein that is uncleaved, whereas in some beta- and all gammacoronaviruses the protein is found cleaved between the S1 and S2 domains, typically by furin, a Golgi-resident host protease. Indeed, the recombinant Spike protein can bind with recombinant ACE2 protein.Ī notable distinction between the spike proteins of different coronaviruses is whether it is cleaved or not during assembly and exocytosis of virions. It's been reported that 2019-nCoV can infect the human respiratory epithelial cells through interaction with the human ACE2 receptor. CoV diversity is reflected in the variable spike proteins (S proteins), which have evolved into forms differing in their receptor interactions and their response to various environmental triggers of virus-cell membrane fusion. The ectodomain of all CoV spike proteins share the same organization in two domains: a N-terminal domain named S1 that is responsible for receptor binding and a C-terminal S2 domain responsible for fusion (Figure 2). Spike proteins assemble into trimers on the virion surface to form the distinctive "corona", or crown-like appearance. In addition, this protein is highly glycosylated as it contains 21 to 35 N-glycosylation sites. The spike protein (S protein) is a large type I transmembrane protein ranging from 1,160 amino acids for avian infectious bronchitis virus (IBV) and up to 1,400 amino acids for feline coronavirus (FCoV) (Figure 1). Industry Insights with Yuning Chen on Recombinant Proteins.ExpertAnswers: Yuning Chen on Antibody Production.Universal Vaccine Advancement through AI and Recombinant Technology.Nanobodies: An Important Tool for the Next Generation of Tumor Diagnostics and Therapeutics.ExpertAnswers: Amy Sheng on Antibody Screening and Discovery.Recombinant DNA Technology and Its Impact on Drug Discovery.CAR-T Cell Therapy Development: From Personalized to off the Shelf Approaches.BioBuzz with Sino | Episode 1: ChatGPT in Biotech.Special Offer: Custom Recombinant Antibody Production Service.Take Our Short Survey to Win Free Gift !.50% OFF: Antibody Humanization Service & AI-Powered Antibody Affinity Maturation Service.Common Cytokine Receptor Signaling Pathway.Multi-pass Transmembrane Protein Development.Beacon ® Single B Cell Screening Service. ![]()
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