Product Overview and Biological Background

CENPS (Centromere Protein S), also known as MHF1 or APITD1, is a histone-fold domain protein that forms a stable heterodimeric complex with CENP-X (MHF2). This CENP-S/CENP-X complex is a conserved component of the inner kinetochore and plays dual roles in centromere chromatin architecture and the DNA interstrand crosslink (ICL) repair pathway, the latter in cooperation with the Fanconi Anemia (FA) pathway.

Recombinant Human CENPS Protein (SKU: rp376824) from Aladdin Scientific is designed to support in vitro biochemical and structural studies, pull-down assays, and functional characterization of centromere-associated complexes. Researchers studying kinetochore assembly, chromosome segregation fidelity, or FA pathway mechanisms will find this reagent particularly relevant.

Reconstitution and Handling Protocol

Reconstitution: Centrifuge the vial briefly (1,000–2,000 × g, 30 seconds) before opening to collect lyophilized material at the bottom. Reconstitute in the buffer recommended on the product datasheet (typically sterile phosphate-buffered saline, PBS, pH 7.4, or a low-salt Tris-based buffer containing a carrier protein such as 0.1% BSA). Add diluent gently along the vial wall and allow to dissolve without vortexing to preserve protein integrity.

Working Concentration: Determine empirically for each assay type. Prepare small single-use aliquots immediately after reconstitution to minimize freeze-thaw degradation.

Handling Precautions: Work on ice at all times. Use low-binding microcentrifuge tubes to reduce adsorption losses. Avoid introducing detergents unless specifically compatible with downstream assays.

Note: Always consult the specific product datasheet provided with each lot for exact buffer composition, concentration, and purity data.

Storage Conditions and Stability

Long-term Storage: Store lyophilized protein at -20°C or -80°C in a frost-free freezer, protected from light and moisture. Under recommended conditions, the lyophilized form is stable for up to 12 months from the date of receipt, though users should verify the expiry date on each lot certificate of analysis.

Reconstituted Protein: Once reconstituted, aliquot immediately and store at -80°C. Avoid storing reconstituted protein at -20°C for extended periods. Reconstituted protein should be used within 1 month when stored at -80°C and within 48 hours when kept at 4°C (on ice).

Freeze-Thaw Cycles: Limit to a maximum of 2–3 freeze-thaw cycles. Repeated freeze-thawing causes aggregation and loss of biological activity. Adding a cryoprotectant such as glycerol (5–10% final concentration) to aliquots may improve stability during frozen storage.

These are general best-practice guidelines for recombinant proteins. Confirm lot-specific recommendations with the product datasheet.

Experimental Applications and Quality Control

Primary Research Applications:

• Protein–Protein Interaction Studies: CENP-S is known to interact with CENP-X; this recombinant protein can be used in co-immunoprecipitation (Co-IP) or pull-down assays to map interaction interfaces.
• Structural Biology: Suitable as a component for crystallography or cryo-EM studies of the CENP-S/X hetero-dimer or larger kinetochore sub-complexes.
• DNA-Binding Assays: The CENP-S/X complex has reported affinity for branched DNA structures; electrophoretic mobility shift assays (EMSA) can be performed to characterize this activity.
• Functional Reconstitution: Use in in vitro nucleosome or CENP-A chromatin reconstitution experiments.

Quality Control: Each lot should be validated by SDS-PAGE and Coomassie staining or Western blot using an anti-CENPS antibody. Endotoxin levels and sterility specifications, where applicable, are listed on the certificate of analysis. Confirm identity by mass spectrometry if high-confidence identification is required.

Troubleshooting Common Issues

Protein Aggregation: If visible precipitation occurs after reconstitution, centrifuge at 10,000 × g for 5 minutes at 4°C and use only the supernatant. Aggregation may indicate improper reconstitution buffer, excessive protein concentration, or thawing at room temperature. Reduce the reconstitution concentration and ensure the buffer ionic strength is appropriate.

Low Activity in Binding Assays: Ensure that all components are at 4°C during assay setup. Check that reducing agents (e.g., DTT or β-mercaptoethanol) are present if required for active conformation. Verify that the protein has not exceeded its recommended storage duration.

Unexpected Bands on SDS-PAGE: Minor bands may represent degradation products or co-purified host-cell proteins. Consult the certificate of analysis for expected purity (%). If purity is insufficient for your application, consider additional purification steps such as size-exclusion chromatography.

Lot-to-Lot Variability: Always run a reference standard alongside new lots in functional assays. Contact Aladdin Scientific technical support if significant variability is observed between lots.