Background and Biological Significance of GLRX5

Glutaredoxin 5 (GLRX5) is a monothiol glutaredoxin localized to the mitochondrial matrix. It belongs to the thioredoxin superfamily and plays an indispensable role in the biogenesis of iron-sulfur (Fe-S) clusters, which are ancient and versatile cofactors required by a broad range of proteins involved in electron transport, DNA repair, and metabolic catalysis.

GLRX5 coordinates a [2Fe-2S] cluster in a glutathione-dependent manner and facilitates the transfer of Fe-S clusters to recipient apoproteins via chaperone-mediated pathways. Loss-of-function mutations in GLRX5 have been linked to sideroblastic anemia in humans and zebrafish models, highlighting its critical role in erythropoiesis and heme metabolism. Additionally, GLRX5 participates in cellular redox homeostasis by modulating the glutathione pool and protecting mitochondrial proteins from oxidative damage.

Recombinant Human GLRX5 Protein (rp369676) enables researchers to investigate these pathways in vitro, serving as a tool for enzyme activity assays, protein-protein interaction studies, and structural biology experiments.

Reconstitution and Storage Protocol

Materials Required: Sterile deionized water or an appropriate aqueous buffer (e.g., 20 mM Tris-HCl, pH 8.0, 150 mM NaCl), microcentrifuge tubes, ice bucket, and a calibrated pipette.

Reconstitution Steps:

1. Allow the lyophilized protein vial to equilibrate to room temperature for 10–15 minutes before opening to prevent condensation.
2. Briefly centrifuge the vial (1,000 × g, 30 seconds) to collect the lyophilizate at the bottom.
3. Add the recommended volume of sterile reconstitution buffer slowly along the inner wall of the vial. Do not vortex; mix gently by pipetting or swirling.
4. Allow the protein to dissolve completely at room temperature for 5–10 minutes, or on ice if the protein is particularly sensitive to temperature.
5. Prepare single-use aliquots to minimize freeze-thaw cycles and snap-freeze in liquid nitrogen prior to long-term storage.

Storage Conditions:

• Long-term: Store at −80°C. Stable for up to 12 months from date of receipt under recommended conditions.
• Short-term working stock: Store at 4°C for up to 1 week. Addition of a carrier protein (0.1% BSA) is recommended if diluting to concentrations below 10 µg/mL.
• Avoid repeated freeze-thaw cycles, as these can cause protein aggregation and loss of activity.

Note: Specific reconstitution volume, buffer composition, and concentration details are provided on the Certificate of Analysis (CoA) supplied with each lot. Always consult the CoA before proceeding.

Experimental Applications and Assay Recommendations

Recombinant Human GLRX5 Protein is suitable for a range of biochemical and cell-free experimental formats. The following applications are commonly pursued in the literature:

1. Iron-Sulfur Cluster Transfer Assays: GLRX5 can be used in reconstituted Fe-S cluster transfer systems to assess its chaperone activity toward downstream target proteins (e.g., BOLA proteins, ferrochelatase). Assays typically involve anaerobic conditions to prevent cluster oxidation. Researchers should use sealed, nitrogen- or argon-purged cuvettes and anaerobic buffers.

2. Glutaredoxin Activity Assays: The deglutathionylation activity of GLRX5 can be measured spectrophotometrically using model substrates such as glutathionylated BSA or β-hydroxyethyl disulfide (HED) in a coupled assay with glutathione reductase and NADPH. Monitor absorbance at 340 nm (NADPH consumption).

3. Protein-Protein Interaction Studies: GLRX5 interacts with scaffold proteins such as ISCU and BOLA3. Pull-down assays, surface plasmon resonance (SPR), or co-immunoprecipitation experiments using His-tagged or GST-tagged variants can be employed to map interaction interfaces.

4. Structural and Biophysical Studies: The recombinant protein can be used for X-ray crystallography, small-angle X-ray scattering (SAXS), or NMR studies to elucidate conformational changes associated with Fe-S cluster binding and transfer.

Recommended Working Concentrations: Consult the lot-specific CoA and relevant primary literature for suggested concentrations. Typical assay concentrations in the literature range from sub-micromolar to low micromolar; however, these must be optimized empirically for each assay format.

Quality Control and Troubleshooting

Quality Control: Each lot of Recombinant Human GLRX5 Protein undergoes standard quality control testing prior to release. Typical QC assessments include SDS-PAGE for purity estimation, Western blot confirmation of identity using anti-GLRX5 antibody, and endotoxin testing by LAL (Limulus Amebocyte Lysate) assay. Refer to the CoA for lot-specific QC data including purity percentage and endotoxin levels.

Common Issues and Solutions:

If issues persist, contact Aladdin Scientific technical support with your lot number and a description of the observed problem.

Safety, Handling Precautions, and Disposal

Safety Classification: Recombinant Human GLRX5 Protein is a research-use-only (RUO) reagent and is not intended for diagnostic, therapeutic, or veterinary use. Standard laboratory safety precautions apply.

Personal Protective Equipment (PPE): Wear appropriate PPE, including lab coat, nitrile gloves, and eye protection when handling the protein. Although GLRX5 is not classified as a hazardous substance, good laboratory practice requires adherence to standard biosafety procedures for handling human-derived recombinant proteins.

Handling Precautions:

• Handle the protein on ice to minimize thermal denaturation during bench work.
• Avoid introducing contaminants such as metal ions that could interfere with Fe-S cluster integrity.
• When performing anaerobic assays, follow your institution's safety guidelines for the use of inert gases (N₂, Ar).

Waste Disposal: Dispose of protein solutions and contaminated consumables in accordance with your institution's biosafety waste disposal regulations. Inactivate before disposal if required by local guidelines (e.g., autoclaving or chemical inactivation).

Regulatory Notice: This product is for research use only. It has not been approved by any regulatory agency for clinical use. Refer to the product's Safety Data Sheet (SDS) for full hazard information.