Recombinant Human MBTPS1 Protein: Research Guide & Applications

Recombinant Human MBTPS1 Protein is a research-grade serine protease corresponding to the human Site-1 Protease (S1P), a Golgi-resident enzyme critical for the proteolytic activation of sterol regulatory element-binding proteins (SREBPs) and other membrane-bound transcription factors involved in cholesterol and lipid homeostasis.

Protein Name

Membrane-Bound Transcription Factor Peptidase, Site 1 (MBTPS1); also known as Site-1 Protease (S1P), SKI-1

UniProt ID

Q14703 (Human)

Enzyme Class

Subtilisin-like serine protease (Proprotein convertase family)

Primary Function

Proteolytic cleavage of SREBPs and ATF6 at the Golgi membrane to activate downstream transcription of lipid biosynthesis genes

Key Substrates

SREBP-1, SREBP-2, ATF6, CREB3 family members, viral glycoproteins

Research Applications

Cholesterol/lipid metabolism, ER stress/UPR studies, viral entry mechanisms, cancer metabolism, SDS-PAGE, Western blot

SKU

rp367885

Biological Background and Mechanism of Action

MBTPS1 (Membrane-Bound Transcription Factor Peptidase, Site 1), commonly designated Site-1 Protease (S1P), is a subtilisin-like serine protease anchored to the luminal face of the Golgi apparatus. It belongs to the proprotein convertase superfamily and plays an indispensable role in the regulated intramembrane proteolysis (RIP) pathway.

The best-characterized substrates of MBTPS1 are the Sterol Regulatory Element-Binding Proteins (SREBPs), master transcriptional regulators of cholesterol, fatty acid, and triglyceride biosynthesis. Under cholesterol-replete conditions, SREBPs are retained at the endoplasmic reticulum (ER) membrane in complex with SCAP and INSIG proteins. When cellular cholesterol is depleted, SCAP escorts SREBPs to the Golgi, where MBTPS1 executes the first cleavage (Site-1) within the luminal loop of the SREBP precursor. This initial cut is an obligatory prerequisite for subsequent Site-2 cleavage by MBTPS2 (S2P), ultimately liberating the N-terminal transcription factor domain to enter the nucleus and upregulate genes encoding LDL receptor, HMG-CoA reductase, and other lipogenic enzymes.

Beyond SREBPs, MBTPS1 cleaves Activating Transcription Factor 6 (ATF6) during ER stress, thereby initiating the unfolded protein response (UPR). It also processes CREB3 family transcription factors and certain viral glycoproteins, illustrating its broad pathophysiological relevance.

Protein Specifications and Quality Attributes

Recombinant Human MBTPS1 Protein (SKU: rp367885) is produced using recombinant expression systems to deliver a research-grade protein suitable for biochemical and cell-free assays. Users should verify the following key quality attributes upon receipt:

• Purity: Recombinant proteins of this class are typically assessed by SDS-PAGE and/or HPLC; confirm lot-specific Certificate of Analysis (CoA) for purity percentage.
• Formulation: Consult the product datasheet for buffer composition, carrier protein additives (e.g., BSA or glycerol), and concentration. Proper formulation is critical for maintaining enzymatic activity during storage and handling.
• Biological Activity: Activity is typically validated using a fluorogenic peptide substrate cleavage assay; refer to lot-specific CoA for specific activity values.
• Endotoxin Level: For cell-based assays, endotoxin content should be verified against the CoA; levels are generally reported in EU/µg.
• Sterility: Confirm sterility specification on the CoA when protein is intended for cell culture applications.

All quality parameters should be reviewed against the lot-specific CoA provided with shipment. Contact Aladdin Scientific technical support for CoA requests or additional characterization data.

Recommended Handling, Storage, and Reconstitution Protocol

Proper handling of Recombinant Human MBTPS1 Protein is essential to preserve enzymatic integrity and experimental reproducibility. Follow these general guidelines:

Receipt and Initial Inspection

• Upon receipt, immediately inspect the vial for physical integrity and confirm that the product was shipped on dry ice or with cold packs as specified.
• Record the lot number and expiry date before storage.

Storage Conditions

• Store lyophilized protein at –20 °C or –80 °C as indicated on the product datasheet. Avoid repeated freeze-thaw cycles, which degrade enzymatic activity.
• Once reconstituted, aliquot into single-use volumes to minimize freeze-thaw exposure.

Reconstitution

• Allow the vial to equilibrate to room temperature for 10–15 minutes before opening to minimize condensation.
• Reconstitute in sterile deionized water or the buffer specified on the datasheet to the recommended stock concentration.
• Gently mix by pipetting; avoid vortexing, which may denature the protein.
• Allow 10 minutes at room temperature after reconstitution to ensure complete dissolution before use or aliquoting.

Working Concentration

• Determine optimal working concentration empirically for each application. Refer to published literature on MBTPS1 activity assays for starting-point guidance.

Note: Always consult the product-specific datasheet (accessible via the product page for rp367885 on the Aladdin Scientific website) for authoritative buffer, concentration, and storage information, as formulations may vary by lot.

Research Applications

Recombinant Human MBTPS1 Protein is a versatile tool across several active research domains:

Cholesterol and Lipid Metabolism

MBTPS1 is the gatekeeper enzyme for SREBP activation. Researchers use recombinant S1P to study enzyme kinetics, screen small-molecule inhibitors targeting dyslipidemia and metabolic syndrome, and validate substrate cleavage sequences in vitro.

ER Stress and Unfolded Protein Response (UPR)

Because MBTPS1 cleaves ATF6 during ER stress, recombinant protein enables biochemical reconstitution of ATF6 processing, supporting studies on ER stress-linked pathologies including diabetes, neurodegeneration, and heart disease.

Viral Entry and Pathogen Biology

MBTPS1 (S1P) has been implicated in priming glycoproteins of several hemorrhagic fever viruses (e.g., Lassa, Ebola). Recombinant MBTPS1 supports in vitro substrate mapping and antiviral inhibitor development.

Cancer Metabolism

Upregulated lipogenesis driven by SREBP activation is a hallmark of many cancers. Studies employing recombinant MBTPS1 contribute to understanding oncogenic lipid reprogramming and may guide therapeutic targeting of the S1P–SREBP axis.

Biochemical Assay Applications

• Fluorogenic peptide cleavage assays for enzymatic characterization
• Western blot and SDS-PAGE as protein-identity controls
• ELISA-based interaction studies with SCAP and other binding partners
• Structural biology (crystallography, cryo-EM) as a recombinant protein source

Troubleshooting and Best Practices

The following guidance addresses common issues encountered when working with Recombinant Human MBTPS1 Protein:

Issue	Likely Cause	Recommended Action
Low or no enzymatic activity	Freeze-thaw degradation; incorrect assay pH or ionic strength; inhibitory components in buffer	Use freshly prepared aliquots; verify assay buffer matches datasheet recommendations; confirm absence of metal chelators (e.g., EDTA) if assay requires divalent cations
Protein aggregation or precipitation	Reconstitution at too-high concentration; incompatible buffer; temperature shock	Reconstitute at recommended concentration; allow equilibration to room temperature before use; centrifuge at low speed to remove aggregates before assay
Unexpected bands on SDS-PAGE	Degradation products; reducing vs. non-reducing conditions mismatch	Compare with CoA reference gel; run under both reducing and non-reducing conditions; ensure protease inhibitor cocktail is used in sample preparation only when MBTPS1 activity is not the target measurement
Inconsistent results between experiments	Lot-to-lot variability; pipetting error at low concentrations	Pre-dilute concentrated stock; use BSA-coated tubes to minimize adsorption; include activity controls in every assay

For persistent issues, contact Aladdin Scientific technical support with the lot number, CoA, and experimental details for expert troubleshooting assistance.

Frequently asked questions

What is the difference between MBTPS1 and MBTPS2, and why does it matter for my experiment?

MBTPS1 (Site-1 Protease, S1P) performs the first luminal cleavage of SREBP precursors within the Golgi, while MBTPS2 (Site-2 Protease, S2P) is an intramembrane metalloprotease that executes the second, intramembrane cut to release the transcription factor domain. MBTPS1 cleavage is an obligatory prerequisite for MBTPS2 activity. If your experiment focuses on reconstituting SREBP processing in vitro, you will need both enzymes in sequence; if you are studying the initial substrate recognition event or performing Site-1 inhibitor screens, Recombinant Human MBTPS1 Protein (rp367885) alone is appropriate.

How should I validate that the recombinant MBTPS1 protein is active before proceeding with my assay?

The most reliable activity validation method is a fluorogenic peptide cleavage assay using a substrate peptide containing the consensus MBTPS1 recognition sequence (typically RXXL or RXXX motif). Measure fluorescence increase over time against a no-enzyme negative control and a known active-enzyme positive control if available. Additionally, review the lot-specific Certificate of Analysis (CoA) provided by Aladdin Scientific, which should include specific activity data from quality control testing. If the protein fails to cleave the reporter substrate, check for buffer incompatibilities, excessive freeze-thaw cycles, or chelating agents that may inhibit serine protease activity.

Can Recombinant Human MBTPS1 Protein be used in cell-based studies?

Recombinant MBTPS1 is primarily designed for biochemical, in vitro, and cell-free assay applications such as substrate cleavage, inhibitor screening, and protein interaction studies. For cell-based studies investigating endogenous SREBP processing or ER stress responses, overexpression vectors or CRISPR-based MBTPS1 knockout/knockin cell models are typically more appropriate. If you intend to introduce recombinant protein into cells via transfection or protein delivery methods, verify endotoxin levels on the CoA and use sterile-filtered protein to avoid confounding inflammatory responses.

What are the key inhibitors of MBTPS1 used in research?

Commonly used MBTPS1 inhibitors in research include the decanoyl-RRLL-chloromethylketone peptide inhibitor (dec-RRLL-CMK) and PF-429242 (a small-molecule competitive inhibitor). These tools are frequently used alongside recombinant MBTPS1 protein to establish inhibition controls in enzymatic assays or to dissect SREBP cleavage in cellular models. Researchers should confirm inhibitor concentrations and selectivity profiles from primary literature before use, as off-target effects at high concentrations have been reported.

How do I order Recombinant Human MBTPS1 Protein from Aladdin Scientific?

Recombinant Human MBTPS1 Protein is listed under SKU rp367885 on the Aladdin Scientific website. You can place an order directly through the online catalog, or contact your regional Aladdin Scientific sales representative or customer service team for bulk pricing, custom formulations, or institutional purchase order arrangements. For technical pre-sales inquiries, the technical support team can provide datasheet, CoA samples, and application-specific guidance.

References

1. Brown MS, Goldstein JL. The SREBP pathway: regulation of cholesterol metabolism by proteolysis of a membrane-bound transcription factor. Cell. 1997;89(3):331-340. doi:10.1016/S0092-8674(00)80213-5
2. Sakai J, Rawson RB, Espenshade PJ, et al. Molecular identification of the sterol-regulated luminal protease that cleaves SREBPs and controls lipid composition of animal cells. Mol Cell. 1998;2(4):505-514. doi:10.1016/S1097-2765(00)80150-1
3. Ye J, Rawson RB, Komuro R, et al. ER stress induces cleavage of membrane-bound ATF6 by the same proteases that process SREBPs. Mol Cell. 2000;6(6):1355-1364. doi:10.1016/S1097-2765(00)00133-7
4. Lenz O, ter Meulen J, Klenk HD, Seidah NG, Garten W. The Lassa virus glycoprotein precursor GP-C is proteolytically processed by subtilase SKI-1/S1P. Proc Natl Acad Sci USA. 2001;98(22):12701-12705. doi:10.1073/pnas.221447598
5. Espenshade PJ, Li WP, Yabe D. Sterols block binding of COPII proteins to SCAP, thereby controlling SCAP sorting in ER. Proc Natl Acad Sci USA. 2002;99(18):11694-11699. doi:10.1073/pnas.182412799

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