Recombinant Human GRPEL2 Protein: Handling & Usage Protocol

Recombinant Human GRPEL2 Protein is a mitochondrial nucleotide exchange factor that serves as an essential co-chaperone of mitochondrial HSP70, and this protocol ensures its correct reconstitution, storage, and application in functional assays.

Product Name

Recombinant Human GRPEL2 Protein

SKU

rp372900

Protein Function

Mitochondrial nucleotide exchange factor; co-chaperone of mitochondrial HSP70 (HSPA9)

Biological Origin

Human (Homo sapiens)

Recommended Storage

-80°C for long-term storage; avoid repeated freeze-thaw cycles

Application

Biochemical assays, mitochondrial chaperone pathway studies, protein-protein interaction studies

Overview of GRPEL2 and Its Biological Role

GRPEL2 (GrpE-like protein 2, mitochondrial) is a nuclear-encoded mitochondrial protein that functions as a nucleotide exchange factor for the mitochondrial Hsp70 chaperone system. It is a mammalian homolog of the bacterial GrpE co-chaperone and plays a critical role in mitochondrial protein import and folding. GRPEL2 facilitates the release of ADP from HSPA9 (mortalin/GRP75), enabling the chaperone cycle to proceed efficiently. Research into GRPEL2 is relevant to understanding mitochondrial proteostasis, stress responses, and diseases linked to mitochondrial dysfunction. Recombinant Human GRPEL2 Protein (rp372900) from Aladdin Scientific provides researchers with a high-quality tool to investigate these pathways in vitro.

Materials and Reagents Required

Before beginning, ensure the following materials are available:

• Recombinant Human GRPEL2 Protein (Aladdin Scientific, SKU: rp372900)
• Ultrapure water or an appropriate reconstitution buffer (e.g., PBS pH 7.4 or 20 mM Tris-HCl, 150 mM NaCl, pH 8.0)
• Low-protein-binding microcentrifuge tubes (1.5 mL)
• Micropipettes and calibrated tips
• Benchtop microcentrifuge
• Spectrophotometer or BCA/Bradford protein assay reagents for concentration verification
• Dry ice and -80°C freezer for storage
• Relevant assay buffers appropriate to downstream application (e.g., ATPase assay buffer for chaperone activity studies)

All equipment should be certified free of RNase/DNase where nucleic acid interactions are being studied. Use freshly prepared buffers whenever possible.

Step-by-Step Reconstitution and Storage Protocol

Follow these steps carefully to maintain protein integrity and biological activity:

1. Thawing: Remove the vial from -80°C storage and allow it to thaw slowly on ice (approximately 10–15 minutes). Do not thaw at room temperature or in a warm water bath, as rapid temperature changes may cause aggregation.
2. Centrifugation: Briefly centrifuge the vial (1,000–2,000 × g for 30 seconds) to collect any condensed material from the cap and walls before opening.
3. Reconstitution: If the product is supplied in lyophilized form, reconstitute by adding the recommended volume of ultrapure water or reconstitution buffer as specified on the product datasheet. Gently pipette up and down to mix; do not vortex vigorously, as shear forces can denature the protein.
4. Concentration Verification: Measure protein concentration using a BCA or Bradford assay. Compare against the certificate of analysis (CoA) value to confirm integrity.
5. Aliquoting: Prepare single-use aliquots to avoid repeated freeze-thaw cycles. A typical aliquot size should be sufficient for one experimental session.
6. Storage: Store aliquots at -80°C for long-term use (up to 12 months from receipt, subject to CoA specifications). For short-term use (up to 1 week), aliquots may be kept at 4°C. Adding a carrier protein such as 0.1% BSA may help stabilize dilute preparations.

Note: Specific reconstitution volumes, buffer compositions, and storage duration should always be confirmed against the product-specific datasheet and certificate of analysis provided with the lot.

Experimental Applications and Working Recommendations

Recombinant Human GRPEL2 Protein is suitable for a range of in vitro biochemical and cell-free studies. Recommended experimental contexts include:

• Mitochondrial HSP70 Chaperone Activity Assays: GRPEL2 can be used as a co-chaperone component alongside HSPA9 to reconstitute the mitochondrial chaperone cycle in vitro. Monitor ATPase activity or substrate refolding as functional readouts.
• Protein–Protein Interaction Studies: Use pull-down assays or co-immunoprecipitation to characterize GRPEL2 binding partners, such as HSPA9 and GRPEL1.
• Structural and Biophysical Studies: Suitable for use in analytical ultracentrifugation, size-exclusion chromatography, or surface plasmon resonance (SPR) experiments to characterize GRPEL2 oligomeric state and binding kinetics.
• Western Blot Standard: Can be used as a positive control or molecular weight standard in immunoblotting experiments with anti-GRPEL2 antibodies.

Working concentrations will depend on the specific assay format. Researchers should optimize concentrations empirically for each application. Consult published literature on GrpE-family proteins for guidance on typical concentration ranges used in analogous systems.

Quality Control and Troubleshooting

To ensure experimental reliability, implement the following quality control checks:

• SDS-PAGE: Run an aliquot on a reducing SDS-PAGE gel to confirm band at the expected molecular weight. A single, prominent band indicates high purity.
• Endotoxin Testing: For cell-based or sensitive biochemical assays, verify endotoxin levels from the CoA. Use limulus amebocyte lysate (LAL) assay if independent verification is required.
• Activity Confirmation: Where possible, include a positive control with a validated lot or a known active preparation to confirm assay system performance.

Common Troubleshooting Issues:

• Protein aggregation: Ensure thawing on ice, avoid vortexing, and confirm buffer compatibility. Centrifuge at 10,000 × g for 5 minutes to remove aggregates before use.
• Loss of activity: Verify storage conditions and number of freeze-thaw cycles. Use freshly thawed aliquots. Consider adding glycerol (5–10%) as a cryoprotectant.
• Low yield after reconstitution: Ensure full dissolution by gently mixing and allowing adequate incubation time. Check pipette calibration.

Frequently asked questions

What is the biological function of GRPEL2?

GRPEL2 is a mitochondrial nucleotide exchange factor and co-chaperone of HSPA9 (mitochondrial HSP70). It facilitates ADP release from HSPA9, enabling the chaperone cycle to proceed and supporting mitochondrial protein import and folding.

How should Recombinant Human GRPEL2 Protein be stored to maintain activity?

The protein should be stored at -80°C for long-term preservation. Repeated freeze-thaw cycles should be avoided by preparing single-use aliquots. For short-term use within one week, storage at 4°C is acceptable. Adding a carrier protein such as 0.1% BSA can help stabilize dilute solutions.

What applications is Recombinant Human GRPEL2 Protein (rp372900) suitable for?

This protein is suitable for in vitro mitochondrial chaperone activity assays, protein-protein interaction studies (pull-down, co-IP), structural and biophysical characterization (AUC, SEC, SPR), and as a Western blot positive control or molecular weight standard when using anti-GRPEL2 antibodies.

How can I verify the quality of the reconstituted GRPEL2 protein before use?

Run an aliquot on a reducing SDS-PAGE gel to confirm the expected molecular weight band and assess purity. Protein concentration should be measured by BCA or Bradford assay and compared to the certificate of analysis. For sensitive assays, endotoxin levels should also be verified.

What should I do if protein aggregation is observed after thawing?

If aggregation is observed, centrifuge the sample at 10,000 × g for 5 minutes at 4°C to pellet aggregates, and use only the clear supernatant. To prevent future aggregation, ensure thawing is done slowly on ice, avoid vortexing, and confirm that the reconstitution buffer is compatible with the protein formulation.

References

1. Saarinen MM et al. Functional characterization of human mitochondrial GrpE-like proteins (GRPEL1 and GRPEL2) as nucleotide exchange factors of mitochondrial Hsp70. [Review flag: specific citation details not confirmed from source material; needs review]
2. Goswami AV et al. Human mitochondrial GrpEL1 and GrpEL2 are functional orthologs of yeast mitochondrial GrpE. [Review flag: specific citation details not confirmed from source material; needs review]
3. Aladdin Scientific. Recombinant Human GRPEL2 Protein, SKU: rp372900. Product Datasheet and Certificate of Analysis.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.