Biological Background of CENPB

Centromere Protein B (CENPB) is a constitutive centromere-associated protein that is evolutionarily conserved among mammals. It is encoded by the CENPB gene and is one of the best-characterized components of the inner kinetochore plate. CENPB recognizes and binds a specific 17-base-pair palindromic sequence known as the CENP-B box, which is found within the alpha-satellite (alphoid) repeat DNA arrays at human centromeres.

CENPB plays a dual role: it contributes to the de novo establishment of centromere chromatin by facilitating the loading of CENP-A (the centromere-specific histone H3 variant), and it helps maintain centromere identity across cell divisions. Although CENPB is absent from the Y chromosome centromere—consistent with the absence of CENP-B boxes on the Y chromosome—it is indispensable for efficient centromere function on autosomes and the X chromosome.

Recombinant Human CENPB Protein produced for research purposes enables direct biochemical interrogation of these functions outside a cellular context, making it a valuable reagent for in vitro studies.

Protein Structure and Key Domains

Human CENPB is approximately 80 kDa in molecular weight and contains several functionally important domains:

• N-terminal DNA-binding domain (DBD): A helix-turn-helix (HTH) motif responsible for specific recognition of the CENP-B box within alpha-satellite DNA. This domain is the most extensively studied region of the protein.
• Dimerization domain (C-terminal): CENPB self-associates through its C-terminal region, forming homodimers that allow simultaneous engagement of two CENP-B box sequences, thereby compacting centromeric chromatin.
• Central linker region: Connects the DNA-binding and dimerization domains, and may participate in interactions with other centromere proteins such as CENP-A nucleosomes and CENP-C.

Understanding the domain architecture of CENPB is essential for designing appropriate in vitro assays when using the recombinant protein, particularly for structural studies or truncation-based functional analyses.

Research Applications

Recombinant Human CENPB Protein (rp365905) is suited for a range of in vitro and biochemical research applications:

• Electrophoretic Mobility Shift Assay (EMSA): Investigate specific binding of CENPB to CENP-B box-containing oligonucleotides or alpha-satellite DNA substrates. This is one of the most common applications for the recombinant protein.
• Chromatin Reconstitution and Pull-down Assays: Assess CENPB interaction with reconstituted CENP-A nucleosomal arrays to study centromere chromatin organization.
• Protein–Protein Interaction Studies: Use co-immunoprecipitation (Co-IP), surface plasmon resonance (SPR), or isothermal titration calorimetry (ITC) to map interactions with inner kinetochore components such as CENP-C and CENP-A.
• Structural Biology: Suitable as a substrate for X-ray crystallography or cryo-electron microscopy (cryo-EM) studies of CENPB–DNA complexes.
• Antibody Production and Validation: Use as an immunogen or positive control antigen for CENPB-specific antibody development and ELISA-based validation.
• Drug and Small-molecule Screening: Evaluate inhibitors that disrupt CENPB–DNA or CENPB–protein interactions relevant to chromosome instability research.

Handling, Storage, and Reconstitution Protocol

Proper handling of Recombinant Human CENPB Protein is critical to preserving activity and preventing aggregation. The following general guidelines apply; always consult the specific product datasheet (absea#PP-12357) for lot-specific instructions:

1. Upon receipt: Inspect the shipment immediately. Store the protein as directed on the datasheet—typically at −70 °C or −80 °C for long-term storage. Avoid storing at −20 °C if repeated freeze-thaw cycles are anticipated.
2. Reconstitution: If supplied lyophilized, reconstitute in sterile ultrapure water or the buffer recommended by the supplier. Centrifuge the vial briefly before opening. Allow the vial to equilibrate to room temperature before adding reconstitution buffer.
3. Aliquoting: Prepare single-use aliquots immediately after reconstitution to minimize freeze-thaw cycles, which can cause irreversible aggregation and loss of DNA-binding activity.
4. Working concentration: Determine empirically for each assay type. Typical EMSA reactions use nanomolar concentrations of CENPB; verify optimal ranges with preliminary titration experiments.
5. Avoid: Repeated freeze-thaw cycles, prolonged storage at 4 °C (>48 hours), and exposure to detergents incompatible with downstream assays.
6. Carrier protein: If the protein concentration is very low, consider adding BSA (0.1%) as a carrier to prevent adsorption to tube walls.

Note: Specific buffer composition, concentration, purity grade, and storage conditions should be confirmed from the official Aladdin product datasheet for rp365905.

Quality Considerations and Experimental Tips

To achieve reproducible and reliable results when working with Recombinant Human CENPB Protein, consider the following:

• Purity verification: Confirm protein purity by SDS-PAGE before critical experiments. A single dominant band at the expected molecular weight (~80 kDa, or the size of the specific construct provided) confirms protein integrity.
• Activity confirmation: Where possible, perform a pilot EMSA with a validated CENP-B box oligonucleotide to confirm DNA-binding activity of each new lot prior to use in high-value experiments.
• Buffer compatibility: CENPB DNA-binding activity may be sensitive to salt concentration and pH. Conduct salt-titration experiments (typically 50–200 mM NaCl or KCl) to identify optimal binding conditions for your specific assay.
• Reducing agents: Include a mild reducing agent such as DTT (1–5 mM) or TCEP (0.5–1 mM) in storage and assay buffers to prevent oxidative aggregation of cysteine residues.
• Lot-to-lot consistency: When changing product lots, re-validate assay conditions, as minor differences in post-translational modifications or truncation of the recombinant construct can affect activity.