Background
We have developed two transmembrane protein display platforms: virus-like particles (VLPs) and nanodiscs. These platforms are designed for functional display of multipass transmembrane proteins in their native conformation. We produce these full-length membrane proteins using detergent-free extraction methods, which preserve the structural integrity and biological activity of the proteins. Our products are suitable for a range of applications including immunization, ELISA, yeast display, flow cytometry, and SPR. For these applications, choose from unlabeled, biotinylated, or fluorescent proteins. Additionally, our transmembrane proteins undergo bioactivity and purity testing using SPR, ELISA, flow cytometry, and HPLC. This ensures functional performance and batch consistency for reproducible results. Researchers can apply these products to antibody discovery, antibody screening, analytical method development, and immunization.
Transmembrane Protein Technology Platforms
Virus-Like Particle (VLP)
Mammalian-expressed transmembrane proteins displayed on VLPs for native conformation and boosted immunogenicity
Copolymer Nanodisc
Transmembrane proteins expressed on membrane-like structures composed of phospholipids and copolymers
Virus-like Particle (VLP) Proteins
Virus-like particles (VLPs) are small nanoparticles composed of virus shell or capsid proteins. These proteins self-assemble into virus-like structures, mimicking the organization and morphology of the actual virus. However, VLPs are absent of viral infectious genomes, making them non-infectious and safe for use in various applications, including antibody immunization, screening, vaccine development and gene therapy.
Mechanism of expression for VLP-displayed antigens.
Advantages of VLP Proteins
VLPs display the target protein in a dense manner on their surface. This boosts the immune response to the target protein, making VLPs useful for immunization, especially with antigens that are usually present in low amounts or don’t trigger a strong immune reaction by themselves. VLPs also allow for the soluble expression of multipass transmembrane proteins without the use of detergents.
Applications
→ Blood sample determination: ELISA
→ In vivo pharmacokinetic analysis
→ Antibody immunization, screening, and functional characterization
→ CMC method development
→ Affinity determination via ELISA, SPR
Features
→ Site-Specific Biotinylation
→ VLP capsid proteins optimized for each protein
→ Proven biological activity via ELISA and SPR
→ Mammalian cell expression system for natural folding and glycosylation
→ Boosted immunogenicity for antibody drug discovery
Product Validation Data
Claudin 18.2 VLP
KACTUS was the first company to express full-length, wild-type Claudin 18.2. This complex 4-transmembrane domain protein has therapeutic potential for gastric and esophageal adenocarcinomas. Despite interest in developing drugs aimed at Claudin 18.2, technical challenges in expressing high-quality Claudin 18.2 protein had limited the potential for antibody drugs around this target. Quality recombinant target proteins are necessary for immunization, screening, and analytical method development. However, by leveraging virus-like particles, we successfully produced full-length Claudin 18.2 protein in mammalian cells. Our consistent activity and purity testing results demonstrate the functional integrity and bioactivity of our VLP-displayed protein platform.
Figure 1. This graph illustrates the intensity distribution of Claudin 18.2 VLPs as measured by dynamic light scattering (DLS). The peak centered at approximately 150 nm indicates a homogeneous population of VLPs, reflecting the consistent size and quality of the particles.
Figure 2. The chromatogram shows the high-performance liquid chromatography (HPLC) profile of Claudin 18.2 VLPs, with a prominent peak observed at 4.909 minutes, indicating the retention time of the Claudin 18.2 protein. The sharp and well-defined peak suggests a high purity and consistency of the VLP preparation.
Figure 3. ELISA assay shows the binding activity of Claudin 18.2 VLPs to anti-Claudin 18.2 antibodies across three different production batches. The consistent curves for Batches 1, 2, and 3 highlight the reproducibility and stability of the VLP preparations. The half-maximal effective concentration (EC50) is determined to be 0.1 nM, indicating high affinity and robust interaction between Claudin 18.2 VLPs and the specific antibodies.
Figure 4. Biolayer Interferometry (BLI) data demonstrates the binding kinetics of Claudin 18.2 VLPs to streptavidin-labeled probes. The analysis reveals a high binding affinity with a dissociation constant (KD) of approximately 5.73E-10 M, indicating strong and stable interaction.
Figure 5. Flow cytometry data demonstrates the binding specificity and quantification of Claudin 18.2 displayed on VLPs. The top panels show the results from HEK293 control cells, while the bottom panels show the results from anti-Cld18.2 CAR-expressing HEK293 cells. The presence of Cld18.2 VLPs results in a significant shift in the fluorescence signal in anti-Cld18.2 CAR-expressing cells, indicating successful detection and quantification of Cld18.2 on VLPs. This validates the high-quality expression and bioactivity of the Claudin 18.2 VLPs.
Figure 6. SPR data showing the binding interactions of Biotinylated Claudin 18.2 VLPs with streptavidin immobilized on a CM5 chip. Results show a dissociation constant (KD) of 1.638E-11 M. This indicates a very strong and stable binding affinity of the Claudin 18.2 VLP.
Nanodisc Proteins
Nanodiscs are small disc-shaped structures that mimic a cell membrane. A target protein is present in a lipid bilayer, which is surrounded by membrane scaffold proteins or copolymers. This discoidal structure enables solubilization without the use of detergents. At KACTUS, we use a proprietary amphipathic copolymer to ensure performance and reliability. Our nanodiscs can be applied in applications such as ELISA, SPR, BLI, and yeast display.
Schematic diagram of nanodisc displaying a multi-transmembrane protein
Advantages of Nanodisc Proteins
Using nanodisc-displayed membrane proteins has several benefits. It maintains the natural conformation of the protein, provides water-soluble proteins, and displays the protein in a native-like environment. Moreover, because nanodiscs can be extracted without detergents, they are superior for membrane proteins that are sensitive to maintaining activity with detergents.
Applications
→ Yeast display screening
→ Functional in vitro assays
→ CAR expression testing
→ PK/PD Studies
→ Analytical Tests, ELISA, SPR, BLI
Features
→ Native protein structure and conformation
→ Detergent-free extraction
→ Water-soluble
→ Proven biological activity via ELISA and SPR
→ Mammalian cell expression system for natural folding and glycosylation
Product Validation Data
GPRC5D Nanodisc
GPRC5D is a complex, 7-transmembrane domain protein and a popular target for multiple myeloma treatment. This protein is being targeted in CAR-T cell therapy, antibody-drug conjugates, and bispecific antibody drugs (with CD3 protein) for myeloma. To facilitate GPRC5D drug development, we have developed a full-length GPRC5D nanodisc with verified bioactivity via ELISA and SPR. Along these lines, we have developed biotinylated nanodisc proteins to broaden use cases for this membrane protein. Our biotinylated GPRC5D nanodisc has high binding activity and can be used in analytical method development and pharmacokinetic analysis.
Figure 7. Human GPRC5D Nanodisc with His Tag was immobilized at 2 µg/ml (100 µl/well) on the plate. The dose-response curve for the Anti-GPRC5D Antibody with hFc Tag was generated, with an EC50 of 4.9 ng/ml as determined by ELISA.
Figure 8. Human CD3E&CD3D, with a His Tag, was immobilized on the plate at a concentration of 2 μg/mL (100 μL/well). Serial dilutions of the Anti-Human CD3×GPRC5D bispecific antibody, with an hFc Tag, were then added, followed by the addition of biotinylated Human GPRC5D Nanodisc, with a His Tag, at 5 μg/mL. Detection was performed using HRP-conjugated streptavidin, and the EC50 was determined to be 0.28 μg/mL by ELISA.
Figure 9. Biotinylated Human GPRC5D Nanodisc, with a His Tag, was loaded onto an SA-Biosensor. This setup was used to determine the binding affinity to the Anti-GPRC5D Antibody, which was measured to be 1.16 nM using a BLI assay.
Figure 10. Human GPRC5D Nanodisc with His Tag was captured on a CM5 Chip via an anti-His antibody. It was found to bind the Anti-GPRC5D Antibody with an affinity constant of 1.47 nM, as determined by SPR assay (Biacore T200).
Available Products
Frequently Asked Questions
KACTUS can provide transmembrane proteins in liquid or lyophilized form. Lyophilized format allows for the use of a custom buffer or adjuvant during screening or immunization as desired. It also ensures stability of the VLP and nanodisc proteins for use in a variety of settings, such as for screening or immunization. Our lyophilization team tests our catalog products for activity after lyophilization, to ensure you are still receiving a bioactive protein.
Generally, VLPs range in size from approximately 20 to 200 nanometers (nm). Their smaller size lets engineered VLPs focus the immune response on specific surface antigens, more so than cell-based immunization.
Our VLPs are produced with high quality standards. Although it is difficult to determine the exact number of copies of the antigen displayed on the surface of the VLP, we take steps to validate each batch of VLPs to assure the displayed protein will have consistency across batches.
To guarantee transmembrane protein quality, KACTUS follows a strict validation process involving various analytical techniques for each batch. This process includes techniques such as size exclusion chromatography, ELISA, and SPR.
Browse the catalog and order directly online via credit card or email us at orders@kactusbio.us to place an order via PO.
Contact us here to request a custom VLP protein.
Our catalog products have a lead time of 2 days to 2 weeks. Custom orders have a turnaround time of 6-8 weeks. Contact us for more information.
Contact us to request more information or set up a meeting with one of our team members.
Related Products & Information
Membrane Protein Products & Services
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VLP & Nanodisc Displayed Transmembrane Proteins | KACTUS