Recombinant Human MCM8 Protein: Handling & Application Protocol

Recombinant Human MCM8 Protein is a eukaryotic DNA replication helicase subunit essential for replisome progression and genomic integrity, supplied by Aladdin Scientific (SKU: rp368213) for use in biochemical, cell-free replication, and functional genomics assays.

Product Name

Recombinant Human MCM8 Protein

SKU

rp368213

Protein Family

Minichromosome Maintenance (MCM) complex, AAA+ ATPase superfamily

Primary Function

DNA replication helicase; roles in DNA repair and meiotic recombination

Recommended Storage

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

Research Applications

DNA replication assays, helicase activity assays, protein interaction studies, reproductive biology research

Background: MCM8 in DNA Replication and Genomic Stability

Minichromosome Maintenance Protein 8 (MCM8) is a member of the conserved MCM family of proteins, which form the catalytic core of the eukaryotic replicative helicase. MCM8, together with MCM9, forms a heterohexameric complex that is functionally distinct from the canonical MCM2–7 replicative helicase complex. The MCM8–MCM9 complex has been implicated in several critical cellular processes, including DNA double-strand break repair via homologous recombination and meiotic recombination.

Loss-of-function mutations in MCM8 are associated with primary ovarian insufficiency (POI) and male infertility in humans, underscoring its physiological importance in gametogenesis. As an AAA+ ATPase family member, MCM8 possesses ATP-binding and hydrolysis activity that drives DNA unwinding, making it a key target for studies of replication stress responses and DNA damage repair pathways.

Recombinant Human MCM8 Protein (rp368213) from Aladdin Scientific enables researchers to investigate these functions in defined biochemical systems, facilitating mechanistic studies without the confounding variables of cell-based approaches.

Reconstitution and Storage Protocol

Materials Required:

• Recombinant Human MCM8 Protein (rp368213)
• Sterile, deionized water or recommended reconstitution buffer (see certificate of analysis for lot-specific guidance)
• Low-binding microcentrifuge tubes
• Ice bucket or cooling block

Reconstitution Steps:

1. Allow the vial to equilibrate to room temperature for 5–10 minutes before opening to minimize condensation and protein aggregation risk.
2. Briefly centrifuge the vial (1,000 × g, 30 seconds) to consolidate lyophilized material at the bottom of the tube.
3. Reconstitute the protein by adding the appropriate volume of sterile reconstitution buffer (refer to the product Certificate of Analysis for the recommended buffer composition and volume) dropwise along the wall of the vial. Do not pipette directly onto the lyophilized cake.
4. Gently swirl or tap the vial to dissolve; do not vortex, as vigorous agitation can denature the protein.
5. Allow the solution to stand on ice for 5 minutes and inspect visually for complete dissolution before use.

Storage Recommendations:

• Short-term (up to 1 week): Store reconstituted protein at 4°C.
• Long-term: Aliquot into single-use volumes and store at −80°C. Avoid repeated freeze-thaw cycles, which can reduce activity and promote aggregation.
• Addition of a carrier protein (e.g., 0.1% BSA) to the storage buffer may improve stability during long-term storage if downstream assay compatibility permits.

Quality Control and Activity Verification

Prior to use in critical experiments, researchers should verify protein identity, purity, and functional activity using the following approaches:

1. SDS-PAGE and Coomassie Staining: Resolve a small aliquot (1–2 µg) under denaturing conditions to confirm the apparent molecular weight matches the expected size for MCM8 (approximately 95–100 kDa for full-length human MCM8, though the exact molecular weight of the recombinant form depends on tags and expression system — refer to the Certificate of Analysis). A single predominant band indicates high purity.

2. Western Blot Verification: Use an anti-MCM8 antibody to confirm protein identity, particularly when band migration appears anomalous on SDS-PAGE. This step is recommended for critical downstream applications.

3. ATPase Activity Assay: MCM8 possesses intrinsic ATPase activity. A colorimetric or radioactive ATPase assay can be used to confirm functional activity of the recombinant protein. Loss of ATPase activity may indicate misfolding or degradation.

4. Protein Concentration Determination: Measure absorbance at 280 nm (A280) using a spectrophotometer or use a Bradford/BCA assay to determine working protein concentration prior to each experiment.

Experimental Applications

Recombinant Human MCM8 Protein (rp368213) is suitable for a range of research applications, including but not limited to:

Helicase and ATPase Assays: Assess the DNA unwinding and ATP hydrolysis activities of MCM8 using fluorescence-based strand-displacement assays or radiolabeled ATP hydrolysis assays. These experiments provide mechanistic insight into how MCM8 contributes to replication fork progression and DNA repair.

Protein–Protein Interaction Studies: Use recombinant MCM8 as bait in pull-down assays, co-immunoprecipitation experiments, or surface plasmon resonance (SPR) analyses to identify and characterize interacting partners, including MCM9 and other replisome or DNA repair components.

Structural Studies: Recombinant MCM8 can serve as material for cryo-electron microscopy (cryo-EM) or X-ray crystallography studies aimed at resolving the structure of the MCM8–MCM9 complex or its interactions with DNA substrates.

Reproductive Biology and Fertility Research: Given the association of MCM8 with primary ovarian insufficiency and male infertility, recombinant protein is useful for in vitro studies examining the molecular consequences of disease-associated MCM8 variants.

Drug Discovery: MCM8 represents a potential therapeutic target. Recombinant protein can be used in screening assays to identify small-molecule inhibitors of MCM8 ATPase or helicase activity.

Troubleshooting and Best Practices

Protein Aggregation: If turbidity is observed after reconstitution, centrifuge at 10,000 × g for 10 minutes at 4°C and use the supernatant. Ensure reconstitution buffer ionic strength and pH are appropriate (refer to the Certificate of Analysis for recommended conditions).

Low Activity: Ensure the protein has not undergone more than one freeze-thaw cycle. Confirm that assay conditions (pH, salt concentration, divalent cation requirements such as Mg²⁺ for ATPase activity) are optimized for MCM8.

Unexpected Bands on SDS-PAGE: Minor bands may represent degradation products or co-purified host-cell proteins. If purity is insufficient for your application, consider additional clean-up steps such as size-exclusion chromatography.

Inconsistent Results Between Lots: Always record the lot number and refer to the lot-specific Certificate of Analysis. Contact Aladdin Scientific technical support if inter-lot variability impacts your research outcomes.

General Best Practices: Work on ice at all times when handling the reconstituted protein. Use low-binding plastic consumables to minimize adsorptive losses. Prepare single-use aliquots immediately after reconstitution to preserve activity.

Frequently asked questions

What is the recommended reconstitution buffer for Recombinant Human MCM8 Protein (rp368213)?

The recommended reconstitution buffer composition and volume are specified in the lot-specific Certificate of Analysis supplied with the product. As a general guideline, a physiological buffer such as PBS (pH 7.4) supplemented with glycerol (5–10%) to stabilize the protein may be appropriate, but researchers should follow the CoA for lot-specific instructions and contact Aladdin Scientific technical support for further guidance.

How many freeze-thaw cycles can Recombinant Human MCM8 Protein withstand without significant loss of activity?

As with most recombinant proteins, it is strongly recommended to limit freeze-thaw cycles to a maximum of one to two cycles. Repeated freezing and thawing promotes protein aggregation and denaturation, which can substantially reduce specific activity. Aliquoting the reconstituted protein into single-use volumes before storage at −80°C is the best practice to preserve biological activity.

What positive control should I use in an MCM8 ATPase activity assay?

A well-characterized ATPase enzyme, such as apyrase or a validated MCM-family protein with known ATPase activity, can serve as a positive control. Alternatively, using a previously validated lot of MCM8 or a known active helicase in your assay system provides a relevant reference. Including an ATP-only (no-enzyme) negative control is equally important to establish baseline hydrolysis levels.

Is Recombinant Human MCM8 Protein suitable for use in cell-free DNA replication assays?

Recombinant Human MCM8 Protein can in principle be used in defined, reconstituted cell-free replication or repair systems designed to study the MCM8–MCM9 complex's role in DNA synthesis or homologous recombination. However, researchers should note that MCM8 functions as part of a multi-protein complex; optimal activity in cell-free systems may require the co-addition of MCM9 and accessory factors. Pilot experiments to optimize protein concentrations and buffer conditions are strongly recommended.

References

1. Lutzmann M, Maiorano D, Méchali M. Identification of full genes and proteins of MCM9, a novel, vertebrate-specific member of the MCM2-8 protein family. Gene. 2005;362:51-56. doi:10.1016/j.gene.2005.07.031
2. Traver S, et al. MCM9 is required for mammalian DNA mismatch repair. Mol Cell. 2015;59(5):831-839. doi:10.1016/j.molcel.2015.07.010
3. AlAsiri S, et al. Exome sequencing reveals MCM8 mutation underlies ovarian failure and chromosomal instability. J Clin Invest. 2015;125(1):258-262. doi:10.1172/JCI78473
4. Aladdin Scientific. Recombinant Human MCM8 Protein, SKU rp368213. Product datasheet. Absea #PP-3237.

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