CoV-2 Spike S1 (200-800)
Description
Receptor Binding and Conformational Dynamics
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The RBD adopts "up" or "down" conformations to regulate ACE2 accessibility. Mutations like D614G stabilize the "up" state, enhancing infectivity .
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Disulfide bonds (e.g., C480–C488) stabilize the RBD structure and enable redox-dependent interactions with host cells .
Hemagglutination and Vascular Effects
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Spike S1 induces red blood cell clumping (hemagglutination) via sialic acid interactions, with Omicron S1 showing 8× greater potency than ancestral strains .
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S1 triggers endothelial and neuronal damage by binding CD147 and glycophorin A, exacerbating COVID-19 complications .
Neurodegenerative Risks
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S1 promotes α-synuclein aggregation in microglial cells, potentially accelerating Parkinson’s disease pathology .
Table 2: Pathological Effects of S1 (200–800)
| Effect | Mechanism | Key Residues/Regions |
|---|---|---|
| Hemagglutination | Sialic acid binding on RBCs | NTD, RBD |
| Endothelial damage | ACE2-independent CD147 interaction | RBD |
| α-Synuclein aggregation | Microglial activation via TLR4 signaling | S1/S2 cleavage site |
Notable Mutations in S1 (200–800)
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E484K (Alpha/Beta/Gamma): Immune evasion by disrupting antibody binding .
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Q954H/N969K/L981F (Omicron): Alters HR1–HR2 interactions but preserves six-helix bundle architecture .
Immune Evasion Strategies
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Omicron S1 accumulates 15 RBD mutations, reducing neutralizing antibody efficacy by >10-fold compared to ancestral strains .
Therapeutic and Diagnostic Applications
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Vaccines: Most vaccines target S1’s RBD to block ACE2 binding .
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Antivirals: Peptides targeting HR1 (e.g., EK1) inhibit fusion across variants .
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Diagnostics: S1-specific antibodies are used in antigen tests, though mutations may reduce accuracy over time .
Unresolved Research Questions
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Does the S1/S2 cleavage site in S1 (residues 682–685) contribute to neuroinvasion observed in long COVID?
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How do S1-induced α-synuclein aggregates persist post-infection?
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Are there conserved epitopes in S1 (200–800) for universal coronavirus vaccines?
Product Specs
In December 2019, a novel coronavirus, designated as 2019-nCoV, emerged in Wuhan, China, causing viral pneumonia in humans. The virus was first identified in connection with a seafood market.
Genetic analysis revealed that 2019-nCoV shares a high degree of similarity (87%) with a bat-derived SARS-like coronavirus (SARS-CoV-2) discovered in Zhoushan, eastern China, in 2018. Despite some genetic variations, the receptor-binding domain (RBD) of 2019-nCoV is structurally similar to that of SARS-CoV, suggesting its potential to bind to the human ACE2 (angiotensin-converting enzyme 2) receptor.
While bats are considered the likely natural reservoir of 2019-nCoV, the intermediary animal responsible for its transmission to humans remains unknown, although seafood sold at the Wuhan market was suspected. Research suggests that 2019-nCoV may be a recombinant virus, with its spike glycoprotein showing evidence of genetic material from both bat coronaviruses and an unidentified coronavirus.
This recombinant protein, expressed in E. coli, encompasses the S1 subunit (amino acids 200-800) of the SARS-CoV-2 Spike protein. It features a C-terminal 6xHis tag for purification and detection purposes.
This product consists of a 1 mg/ml solution of the CoV 2019 Spike S1 (200-800 a.a.) Protein. It is formulated in 1x PBS (phosphate-buffered saline).
The CoV 2019 Spike S1 (200-800 a.a.) Protein is shipped with ice packs to maintain its stability. Upon receipt, it should be stored at -20°C (-4°F).
The purity of the CoV 2019 Spike S1 Protein is greater than 90%, as determined by SDS-PAGE analysis.
Q&A
What experimental models are most suitable for studying Spike S1-induced cellular injury?
Rat alveolar type II-like (L2) epithelial cells serve as a robust model for investigating Spike S1's ACE2-independent effects. These cells lack functional ACE2 receptors but exhibit proteomic changes in E2F1, CREB1, and RhoA/ROCK2 pathways upon S1 exposure . Key methodological steps include:
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Culture conditions: Maintain L2 cells in Ham’s F-12K medium with 10% FBS at 37°C/5% CO₂.
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S1 treatment: Apply recombinant Spike S1 (200-800) at 50 nM for 24 hours.
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Proteomic analysis: Use liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a 1.5–2.0-fold change threshold for significance .
Table 1: Proteomic Changes in L2 Cells Post-S1 Exposure
| Pathway | Upregulated Proteins | Downregulated Proteins | Fold Change | p-value |
|---|---|---|---|---|
| E2F1 Signaling | Cyclin D1, CDK6 | p21, p27 | +2.3 | 0.003 |
| RhoA/ROCK2 | MYPT1, LIMK2 | Cofilin, MLC2 | +1.8 | 0.01 |
How can researchers confirm Spike S1’s ACE2-independent mechanisms?
Three experimental strategies validate ACE2-independent pathways:
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ACE2-negative cell lines: Use L2 cells (rat origin) with negligible ACE2 expression .
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Receptor blockade: Pre-treat cells with ACE2 inhibitors (e.g., MLN-4760) and measure residual S1 binding via flow cytometry.
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Alternative receptor targeting: Quantify S1 binding to CD147, TLR4, or ASGR1 using surface plasmon resonance (SPR) with KD values <10 nM .
What molecular mechanisms link Spike S1 to sustained neuroinflammation?
Spike S1 activates TLR4 signaling in microglia, inducing synaptic phagocytosis and cognitive impairment. Methodological validation involves:
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Intracerebroventricular (i.c.v.) infusion: Administer 2 µg S1 in mice via osmotic pump for 7 days .
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Behavioral assays: Use Morris water maze (latency: 45 ± 8 sec vs. 22 ± 5 sec in controls; p<0.01) and Y-maze (alternation rate: 58% vs. 82%; p<0.05) at 30–60 days post-infusion .
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Microglial profiling: Quantify C1q-positive synapses (↑2.1-fold; p=0.004) and TMEM119+ cell density (↑37%; p=0.01) via immunohistochemistry .
Figure 1: TLR4-KO mice show attenuated synaptic loss (p=0.03) versus wild-type, confirming TLR4’s role in S1-induced neurodegeneration .
How does Spike S1 exacerbate angiotensin II (ANG II)-induced hypertension?
Central S1 priming dysregulates Nrf2-mediated antioxidant responses in the paraventricular nucleus (PVN):
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Experimental design:
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Phase 1: Inject 500 ng S1 intracisternally for 5 days.
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Phase 2: Subcutaneous ANG II (200 ng/kg/min) for 14 days.
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Outcomes:
Table 2: PVN Molecular Markers Post-S1/ANG II
What structural modifications improve Spike S1 stability for immunological studies?
The VFLIP construct enhances stability through:
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Proline substitutions: K986P/V987P stabilizes prefusion conformation (Tm = 58°C vs. 49°C wild-type) .
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Disulfide bonds: Cys991-Cys994 crosslinks protomers (90% trimer retention after 7 days at 4°C) .
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Glycan profiling: LC-MS/MS confirms native-like glycosylation at N331 and N343 .
Applications:
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Antibody binding: VFLIP shows 8.3 nM affinity for COVOX-253 vs. 12.4 nM for wild-type .
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Vaccine immunogenicity: Murine models yield neutralizing titers of 1:1,280 against B.1.351 .
How to resolve contradictions in Spike S1’s inflammatory effects across studies?
Discrepancies arise from:
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Dose-dependent responses: S1 at 10 nM activates TLR2/4, while 50 nM induces pyroptosis .
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Temporal factors: Acute exposure (24h) upregulates IL-6 transiently, whereas chronic exposure (7d) sustains TNF-α .
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Solution: Standardize dosing (10–100 nM) and assay timelines in publication guidelines.
What controls are essential for in vivo S1 studies?
Product Science Overview
The Coronavirus 2019 Spike S1 (200-800 a.a.) Recombinant is a crucial component in the study and understanding of the SARS-CoV-2 virus, which causes COVID-19. This recombinant protein is a segment of the spike protein, specifically the S1 subunit, which plays a vital role in the virus’s ability to infect host cells.
The spike protein of SARS-CoV-2 is a transmembrane protein that protrudes from the viral surface, giving the virus its characteristic crown-like appearance. The spike protein is divided into two subunits: S1 and S2. The S1 subunit contains the receptor-binding domain (RBD), which is responsible for binding to the host cell receptor, angiotensin-converting enzyme 2 (ACE2). This binding is the first step in the viral entry process.
The recombinant form of the spike protein, specifically the S1 subunit (200-800 amino acids), is produced using recombinant DNA technology. This involves inserting the gene encoding the spike protein into an expression system, such as bacteria or mammalian cells, to produce the protein in large quantities.
The recombinant spike S1 protein is used in various research and diagnostic applications:
- Vaccine Development: The spike protein is a primary target for vaccine development because it is the main antigen that elicits an immune response. Recombinant spike proteins are used to develop subunit vaccines, which contain only the antigenic parts of the virus.
- Diagnostic Assays: The recombinant spike S1 protein is used in serological assays to detect antibodies against SARS-CoV-2 in patient samples. These assays help determine whether an individual has been exposed to the virus and has developed an immune response.
- Therapeutic Research: Researchers use the recombinant spike protein to study the interaction between the virus and the host cell receptor. This research is crucial for developing therapeutic agents that can block viral entry and prevent infection.
The production of recombinant spike S1 protein involves several steps:
- Gene Cloning: The gene encoding the spike protein is cloned into an expression vector, which is then introduced into an expression system such as E. coli or HEK293 cells.
- Protein Expression: The expression system produces the spike protein, which is then harvested from the cells.
- Purification: The recombinant protein is purified using techniques such as affinity chromatography, which isolates the protein based on its specific binding properties.
