Recombinant full-length soluble trimeric SARS-CoV-2 D614G variant
The original Wuhan strain of COVID-19 is no longer the dominant circulating virus in the global pandemic. A variant carrying a D614G mutation in the Spike (S) protein of SARS-CoV-2 emerged at an early stage of the pandemic and has now become the prevalent form (1). Korber et al reported that this D614G variant may be more virulent with increased patient viral loads, but is not associated with a more severe disease outcome. According to Grubaugh et al, the impact of this mutation on the global pandemic is as yet unknown and will require further investigation (2).
Image from Korber et al, 2020
New to the market and made in the UK
Daresbury Proteins Limited are excited to announce the launch of their recombinant full-length trimeric soluble SARS-CoV-2 Spike protein D614G variant. A soluble recombinant protein with a foldon trimerization motif, mutated Furin recognition site and 2 stabilising mutations (K986P and V987P), based on/modified from Amanat et al, 2020 (3).
The D614G mutation is located in the S1 subunit of the Spike protein. The S protein monomer consists of two active subunits, the S1 subunit which binds the host receptor and the S2 subunit which facilitates fusion of viral and host cell membranes. The S protein monomers combine to form the distinctive homotrimers which project from the viral cell surface. Viral entry into the host cell is via the ACE2 receptors located on the host cell membrane (4), (5). The spike protein is highly immunogenic and most of the vaccines and therapeutic agents currently in development target this region.
Daresbury Proteins are a UK-based emerging biotech, specialising in authentic mammalian proteins for high-end applications. Focussed on quality, Daresbury Proteins offers a catalogue of histidine-tagged recombinant human proteins for research, clinical and diagnostic applications. The highly validated recombinant full-length trimeric SARS-CoV-2 Spike protein, D614G variant (amino acids 16-1213) is produced in HEK293 cells and supplied in liquid format. Endotoxin levels are less than 0.1 ng/µg (1 IEU/µg), and purity >90% as estimated by SDS-PAGE. A C-terminal 8x histidine Tag has been added to the protein for ease of use.
SDS-PAGE of Recombinant SARS-CoV-2 Spike protein, D614G variant stained with Instant Blue Stain (Expedeon).
(1) Korber et al., Tracking Changes in SARS-CoV-2 Spike: Evidence that D614G Increases Infectivity of the COVID-19 Virus, Cell (2020), https://doi.org/10.1016/j.cell.2020.06.043
(2) Grubaugh et al., Making Sense of Mutation: What D614G Means for the COVID-19 Pandemic Remains Unclear, Cell (2020), https://doi.org/10.1016/j.cell.2020.06.040
(3) Amanat, F., Stadlbauer, D., Strohmeier, S., et al. A serological assay to detect SARS-CoV-2 seroconversion in humans. Nat Med., 2020;26:1033–1036.
(4) Walls et al., Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein 2020, Cell, 180, 281–292
(5) Hoffmann M., Kleine-Weber H., Schroeder S., et al. SARS-CoV-2 Cell Entry Depends on ACE2 and TMPRSS2 and Is Blocked by a Clinically Proven Protease Inhibitor. Cell, 2020;181(2):271-280.
SARS-CoV-2 D614G variant spike protein
Daresbury Proteins reports additional validation data for its recombinant full-length trimeric SARS-CoV-2 D614G variant spike protein. In-depth analysis of the spike protein by Circular Dichroism (CD) spectroscopy confirms correct secondary structure and trimeric assembly. Two different batches of S protein were tested; the first batch in PBS buffer and the second batch in PBS buffer with 20% glycerol. The gel filtration profile demonstrates correct protein size and a lack of aggregation whether stabilised by the protectant glycerol or not. Differential scanning fluorimetry data of the two batches shows the protein is both stable and functional, with heparin binding activity.
Figure 1. CD spectra of different cation forms of spike protein.
A and C, CD spectra were recorded on J-1100 spectrometer between 180 and 260 nm of spike protein
(0.5 mg/mL). B and D, Secondary structure were analysed by program CDSSTR of (A/C). A and B is the first
batch of spike protein (PBS buffer), C and D is the second batch of spike protein (PBS 20% Glycerol).
Figure 2. Differential scanning fluorimetry (DFS) analysis the stability and the heparin binding ability.
DSF of proteins were performed in the absence or presence of heparin (10μM). A and B is the first batch of spike protein (PBS), C and D is the second batch of spike protein (PBS 20% Glycerol). A and C, Melting curve of spike protein. B and D, First derivative of the melting curves of spike to show its melting temperature as peak.
Figure 3. Gel filtration on BSA, Spike 1 (the first batch, in PBS buffer) and Spike 2
(the second batch, in PBS buffer and 20% Glycerol).