Recombinant Human GPA33 Protein: Key FAQs & Applications
Recombinant Human GPA33 Protein: Key FAQs & Applications
Recombinant Human GPA33 Protein is a recombinantly produced form of the human glycoprotein A33 antigen, a type-I transmembrane protein predominantly expressed in gastrointestinal epithelium and widely studied as a colorectal cancer biomarker and therapeutic target.
- Product Name
- Recombinant Human GPA33 Protein
- SKU
- rp368033
- Protein Family
- Immunoglobulin superfamily (IgSF), junction adhesion molecule-related
- Primary Expression Site
- Gastrointestinal epithelium, highly expressed in colorectal tissue
- Key Research Application
- Colorectal cancer research, antibody validation, immunotherapy target studies
- Protein Origin
- Human (Homo sapiens)
What Is GPA33 and Why Is It Scientifically Important?
GPA33 (Glycoprotein A33), also known as the A33 antigen, is a type-I transmembrane glycoprotein belonging to the immunoglobulin superfamily. It is encoded by the GPA33 gene and is characterized by two extracellular immunoglobulin-like domains, a single transmembrane domain, and a short cytoplasmic tail.
GPA33 is constitutively and homogeneously expressed in the epithelial cells lining the gastrointestinal tract from the small intestine to the colon. Its highly restricted and stable expression pattern—maintained in over 95% of primary and metastatic colorectal cancers—makes it a compelling biomarker and therapeutic target in colorectal cancer research. It has been investigated in the context of antibody-drug conjugates (ADCs), radioimmunotherapy, and bispecific antibody approaches.
Understanding GPA33 biology is relevant to researchers working in gastrointestinal oncology, epithelial cell biology, and tumor immunology.
What Are the Typical Research Applications of Recombinant Human GPA33 Protein?
Recombinant Human GPA33 Protein supports a broad range of in vitro and biochemical research applications, including:
- Antibody Development and Validation: Used as an immunogen or coating antigen in ELISA to develop, screen, and validate anti-GPA33 antibodies for research and therapeutic purposes.
- Binding and Interaction Studies: Enables assessment of protein–protein or protein–antibody binding kinetics using surface plasmon resonance (SPR), biolayer interferometry (BLI), or pull-down assays.
- Functional Assays: Supports investigation of GPA33 involvement in epithelial cell adhesion and paracellular permeability regulation.
- Immunotherapy Research: Serves as a reference standard for evaluating ADC payloads, CAR-T cell constructs, or bispecific antibodies targeting GPA33 in colorectal cancer models.
- Western Blot and ELISA Standards: Acts as a positive control or quantitative standard in immunoassays designed to detect endogenous GPA33.
Researchers should confirm suitability for specific assay formats based on the protein's formulation and tag configuration.
How Should Recombinant Human GPA33 Protein Be Stored and Handled?
Proper storage and handling of recombinant proteins are critical to maintaining their biological activity and structural integrity. General best-practice guidelines for Recombinant Human GPA33 Protein include:
- Long-term storage: Store at −80 °C to preserve full activity. Avoid repeated freeze-thaw cycles, as these can cause protein aggregation and activity loss.
- Short-term storage: If the protein will be used within 1–2 weeks, aliquots may be stored at −20 °C or 4 °C depending on the supplied formulation buffer.
- Aliquoting: Upon receipt, divide the protein into single-use aliquots to minimize freeze-thaw stress.
- Reconstitution: If supplied lyophilized, reconstitute with the recommended diluent (typically sterile water or PBS) as specified in the product datasheet. Allow the vial to equilibrate to room temperature before opening.
- Avoid: Repeated freeze-thaw cycles, extended incubation at room temperature, and exposure to detergents incompatible with downstream assays.
Always refer to the specific product datasheet for Aladdin SKU rp368033 for confirmed storage conditions, buffer composition, and shelf life.
Quality, Purity, and Expression System Considerations
The quality of a recombinant protein directly impacts experimental reproducibility and data reliability. When evaluating Recombinant Human GPA33 Protein, researchers should consider the following parameters:
- Expression System: Recombinant GPA33 proteins are typically produced in mammalian (e.g., HEK293) or insect cell systems to preserve post-translational modifications such as glycosylation, which is particularly relevant for a glycoprotein like GPA33. Prokaryotic expression systems (e.g., E. coli) may yield non-glycosylated forms suitable for certain structural or antibody-screening studies.
- Purity: Research-grade recombinant proteins are generally supplied at ≥90% purity as assessed by SDS-PAGE. Confirm the exact purity specification on the product datasheet for rp368033.
- Endotoxin Level: For cell-based or in vivo studies, low endotoxin levels are essential. Check the datasheet for LAL-tested endotoxin values.
- Tag Configuration: The protein may carry an affinity tag (e.g., His-tag, Fc-tag) to facilitate purification. The presence and position of any tag should be considered when designing binding or functional assays, as tags may influence protein conformation or binding interfaces.
Contact Aladdin Scientific technical support for a certificate of analysis (CoA) confirming lot-specific quality attributes.
Frequently asked questions
What is the biological function of GPA33 in normal human tissue?
GPA33 is a transmembrane glycoprotein expressed constitutively in gastrointestinal epithelial cells, where it is believed to play roles in cell–cell adhesion and regulation of paracellular permeability, similar to other members of the immunoglobulin superfamily involved in tight junction organization. Its precise signaling role in normal epithelium remains an area of active investigation.
Why is GPA33 considered a valuable colorectal cancer target?
GPA33 is expressed in a high proportion of primary and metastatic colorectal cancers with minimal expression in most non-gastrointestinal normal tissues, giving it a favorable tumor-to-normal tissue expression ratio. This restricted expression profile reduces the risk of off-target toxicity in antibody-based therapeutic strategies and makes GPA33 an attractive target for radioimmunotherapy, antibody-drug conjugates, and bispecific antibodies in colorectal cancer.
Can Recombinant Human GPA33 Protein be used as an ELISA coating antigen for antibody screening?
Yes, recombinant GPA33 protein is commonly used as a coating antigen in ELISA formats to screen hybridoma supernatants or phage-display libraries for anti-GPA33 antibody clones. Researchers should optimize coating concentration, blocking conditions, and detection reagents empirically. Refer to the product datasheet for rp368033 for recommended working concentrations and compatible assay conditions.
Does glycosylation matter when selecting Recombinant Human GPA33 Protein for my experiment?
Yes, glycosylation can be functionally significant for GPA33, as it is a glycoprotein in its native form. For experiments requiring native-like epitopes—such as antibody epitope mapping, receptor binding studies, or cell-based assays—mammalian-expressed recombinant GPA33 with authentic glycosylation is preferred. For structural studies or applications where glycosylation is less critical, non-glycosylated forms from prokaryotic expression may be acceptable. Check whether rp368033 is produced in a glycosylation-competent system in the product datasheet.
How do I minimize protein degradation when working with Recombinant Human GPA33 Protein?
To minimize degradation, always work on ice when the protein is thawed, use low-protein-binding tubes and pipette tips, add protease inhibitor cocktail to working solutions if appropriate for your assay, and avoid vortexing (instead, gently pipette to mix). Pre-aliquot upon receipt to prevent repeated freeze-thaw cycles, and do not leave reconstituted protein at room temperature for extended periods.
References
- Heath JK, White SJ, Johnstone CN, et al. The human A33 antigen is a transmembrane glycoprotein and a novel member of the immunoglobulin superfamily. Proc Natl Acad Sci USA. 1997;94(2):469-474.
- Ritter G, Cohen LS, Nice EC, et al. Characterization of posttranslational modifications of human A33 antigen, a novel palmitoylated surface glycoprotein of human gastrointestinal epithelium. Biochem Biophys Res Commun. 1997;236(3):682-686.
- Scott AM, Lee FT, Jones R, et al. A phase I trial of humanized monoclonal antibody A33 in patients with colorectal carcinoma: biodistribution, pharmacokinetics, and quantitative tumor uptake. Clin Cancer Res. 2005;11(13):4810-4817.
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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