The Activin type I receptors transduce signals for a variety of members of the Transforming growth factor beta superfamily of ligands. This family of cytokines and hormones include activin, Anti-müllerian hormone (AMH), bone morphogenetic proteins (BMPs), and Nodal. They are involved in a host of physiological processes including, growth, cell differentiation, homeostasis, osteogenesis, apoptosis and many other functions. There are three type I Activin receptors: ACVR1, ACVR1B, and ACVR1C. Each bind to a specific type II receptor-ligand complex.
Despite the large amount of processes that these ligands regulate, they all operate through essentially the same pathway: A ligand binds to a Type two receptor, which recruits and trans-phosphorylate a type I receptor. The type I receptor recruits a receptor regulated SMAD (R-SMAD) which it phosphorylates. The RSMAD then translocates to the nucleus where it functions as a transcription factor. Activin isoforms and other members of the TGF-β superfamily exert their biological effects by binding to heteromeric complexes of a type I and a type II serine-threonine kinase receptor, both of which are essential for signal transduction. To date, seven type I and
five type II receptors, including the two type I and the two type II activin receptors, designated ActR-I(A), ActR-IB, ActR-II(A) and ActR-IIB, have been cloned from mammals. Through alternative mRNA splicing, multiple ActR-IIB isoforms can also be generated, adding to the complexity of the activin receptor system. Different activin isoforms bind with different high-affinities to the various type II isoforms. Type I activin receptors do not bind directly to activin but will associate with the type II receptor-activin complex and
initiate signal transduction. Besides the activin isoforms, ActR-II will also bind inhibin, BMP-2 and BMP-7 with lower affinities. ActR-I can also bind and form signaling complexes with the BMP-2/7-bound BMPR-II. Activin type I receptors are highly conserved. Human, mouse and bovine type IA activin receptors share greater than 98% amino acid sequence homology. Recombinant soluble activin type I receptor does not bind activin.
The predicted molecular weight of Recombinant Human Activin RIA is 39 kDa & 28 kDa (monomers). However, the actual molecular weight as observed by migration on SDS Page is 40-45 kDa & 34-38 kDa.
Predicted Molecular Mass
39
Formulation
This recombinant protein was 0.2 µm filtered and lyophilized from modified Dulbecco’s phosphate buffered saline (1X PBS) pH 7.2 – 7.3 with no calcium, magnesium, or preservatives.
Storage and Stability
This lyophilized protein is stable for six to twelve months when stored desiccated at -20°C to -70°C. After aseptic reconstitution, this protein may be stored at 2°C to 8°C for one month or at -20°C to -70°C in a manual defrost freezer. Avoid Repeated Freeze Thaw Cycles. See Product Insert for exact lot specific storage instructions.
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Recombinant Human ALK-2 is a valuable tool in research applications focused on understanding and modulating the BMP-SMAD signaling pathway, iron metabolism, bone formation, and disease models involving ALK2 dysregulation.
Key scientific applications and rationale:
Mechanistic Studies of BMP-SMAD Pathway: ALK-2 (also known as ACVR1) is a type I receptor for bone morphogenetic proteins (BMPs), central to the BMP-SMAD signaling cascade. Recombinant ALK-2 enables in vitro assays to dissect ligand-receptor interactions, downstream signaling, and transcriptional regulation, particularly of genes like hepcidin involved in iron homeostasis.
Iron Metabolism and Anemia Research: ALK-2 regulates hepcidin transcription, a key hormone controlling systemic iron levels. Recombinant ALK-2 is used to study hepcidin regulation in hepatocytes and to screen for molecules (e.g., antibodies, inhibitors) that modulate ALK-2 activity, with direct relevance to anemia of inflammation and chronic kidney disease models.
Bone Biology and Regeneration: ALK-2 is implicated in osteogenic differentiation and bone regeneration. Recombinant ALK-2 is essential for in vitro differentiation protocols, screening osteoinductive compounds, and modeling disorders such as fibrodysplasia ossificans progressiva (FOP).
Drug Discovery and Screening: Recombinant ALK-2 protein is used in biochemical assays to identify and characterize small molecule inhibitors or neutralizing antibodies, which are being developed for conditions like FOP, certain cancers (e.g., DIPG), and anemia. It allows for high-throughput screening and selectivity profiling against related kinases (e.g., ALK5).
Disease Modeling: Recombinant ALK-2 is used to generate cellular and animal models expressing wild-type or mutant ALK2, facilitating studies of disease mechanisms and therapeutic interventions, especially in genetic disorders and cancer.
Best practices for use:
Employ recombinant ALK-2 in ligand-binding assays, kinase activity assays, and cell-based functional studies to elucidate its role in signaling and disease.
Use recombinant ALK-2 as a standard or control in ELISA, Western blot, and flow cytometry to validate antibody specificity and quantify receptor expression.
Integrate recombinant ALK-2 in co-culture or differentiation protocols to study its effects on stem cells, osteoblasts, or hepatocytes.
Summary of scientific value:
Using recombinant human ALK-2 in research provides a controlled, reproducible means to study its biological functions, screen for therapeutic agents, and model diseases where ALK2 is a critical regulator. This approach accelerates mechanistic insights and translational applications in hematology, bone biology, and targeted therapy development.
You can use recombinant human ALK-2 as a standard for quantification or calibration in your ELISA assays, provided that the recombinant protein is well-characterized, its concentration is accurately determined, and it is compatible with your assay’s antibodies and detection system.
Key considerations and best practices:
Protein Characterization: Ensure the recombinant ALK-2 is of high purity (typically >95% by SDS-PAGE) and that its concentration has been reliably quantified, for example by BCA assay or absorbance at 280 nm.
Epitope Compatibility: The recombinant ALK-2 must contain the relevant epitopes recognized by the capture and detection antibodies in your ELISA. If your antibodies are specific to post-translational modifications or conformational epitopes present only in the native protein, recombinant standards may not be detected equivalently.
Standard Curve Preparation: Prepare a serial dilution of the recombinant ALK-2 in the same buffer or matrix as your samples (e.g., PBS with BSA or serum/plasma) to minimize matrix effects and ensure accurate quantification.
Validation: Validate the use of recombinant ALK-2 as a standard by assessing recovery, linearity, and parallelism between the standard curve and endogenous ALK-2 in your sample matrix. Ideally, spike known amounts of recombinant ALK-2 into negative samples and confirm that the assay accurately recovers the spiked protein.
Documentation: Record the lot number, concentration, and storage conditions of your recombinant standard for reproducibility and traceability.
Caveats:
Some ELISA kits are optimized for detection of native proteins and may not guarantee equivalent detection of recombinant proteins due to possible differences in sequence, folding, or post-translational modifications.
Always check the product datasheet and, if possible, consult the antibody or kit manufacturer’s technical support for compatibility with recombinant standards.
Summary Table:
Requirement
Recombinant ALK-2 Standard Use
High purity
Required
Accurate quantification
Required
Epitope compatibility
Required
Matrix matching
Recommended
Validation (recovery, etc)
Required
In summary, recombinant human ALK-2 can be used as a standard in ELISA quantification, but you must validate its performance in your specific assay context and ensure it is detected equivalently to the native protein.
Recombinant Human ALK-2 (Activin receptor type I, ACVR1) has been validated for several key applications in published research, primarily in enzyme kinetics, inhibitor screening, selectivity profiling, and mechanistic studies of iron metabolism and anemia.
Validated Applications:
Enzyme Kinetics: Recombinant ALK-2 is widely used to study its kinase activity, allowing researchers to characterize catalytic parameters and substrate specificity.
Inhibitor Screening and Selectivity Profiling: It serves as a target for high-throughput screening of small molecule inhibitors, including selectivity profiling against related kinases, which is crucial for drug discovery efforts targeting ALK-2 in diseases such as fibrodysplasia ossificans progressiva (FOP), certain cancers, and anemia of inflammation.
Protein-Protein Interaction Studies: Recombinant ALK-2 is used in binding assays to investigate interactions with ligands (e.g., BMPs) and neutralizing antibodies, such as in surface plasmon resonance (SPR) and biolayer interferometry (BLI) experiments.
Cell Signaling and Mechanistic Studies: It is employed in cell-based assays to elucidate the role of ALK-2 in the BMP-SMAD pathway, particularly in regulating hepcidin transcription and iron homeostasis. For example, recombinant ALK-2 was used to demonstrate the mechanism of a neutralizing antibody (RKER-216) in suppressing hepcidin and alleviating anemia in mouse models.
Disease Modeling and Therapeutic Research: Recombinant ALK-2 has been used in preclinical studies to model and investigate therapeutic approaches for conditions such as FOP, diffuse intrinsic pontine gliomas (DIPGs), ependymomas, endometrial cancer, atherosclerosis, and various forms of anemia.
Structural and Biophysical Characterization: Recombinant ALK-2 is utilized for crystallography, NMR, and other structural studies to understand its conformation and ligand-binding properties, which inform rational drug design.
Functional Assays in Developmental Biology: ALK-2 is involved in growth, differentiation, osteogenesis, and apoptosis, and recombinant protein is used to study these processes in vitro.
Summary Table of Validated Applications
Application Area
Example Use Case/Assay Type
Reference(s)
Enzyme kinetics
Kinase activity assays
Inhibitor screening
High-throughput drug screening
Selectivity profiling
Kinase panel profiling
Protein-protein interaction
SPR, BLI, antibody binding assays
Cell signaling studies
BMP-SMAD pathway, hepcidin regulation
Disease modeling/therapeutics
FOP, anemia, cancer models
Structural characterization
Crystallography, NMR
Functional assays (developmental)
Growth, differentiation, osteogenesis studies
Additional Notes:
Recombinant ALK-2 is typically expressed with tags (e.g., GST) for purification and assay compatibility.
It is used as a standard or control in immunoassays and for calibration in quantitative studies.
Research applications are strictly for non-clinical, non-diagnostic purposes.
If you require protocols or specific assay formats for any of these applications, please specify the intended use.
To reconstitute and prepare Recombinant Human ALK-2 (ACVR1) protein for cell culture experiments, dissolve the lyophilized protein in sterile water or buffer to a concentration of 0.1–1.0 mg/mL, then dilute as needed in cell culture medium or buffer containing a carrier protein such as 0.1% BSA to minimize adsorption and maintain stability.
Step-by-step protocol:
Centrifuge the vial: Briefly spin down the lyophilized protein to collect all material at the bottom.
Reconstitution:
Add sterile, ice-cold deionized water or 1× PBS to achieve a final concentration of 0.1–1.0 mg/mL.
Gently swirl or invert the vial to dissolve. Avoid vigorous vortexing or pipetting to prevent protein denaturation.
Carrier protein addition (recommended for cell culture use):
Dilute the reconstituted protein in buffer containing 0.1% BSA, 10% FBS, or 5% HSA to stabilize the protein and prevent loss from adsorption to plasticware.
Aliquoting and storage:
Aliquot the solution to avoid repeated freeze-thaw cycles.
Store aliquots at −20°C to −80°C for long-term storage (up to 3 months), or at 4–8°C for short-term use (2–7 days).
Working solution:
Before adding to cell culture, dilute the protein to the desired working concentration in pre-warmed culture medium containing carrier protein.
Filter sterilize if necessary, using a 0.2 μm filter, especially if the protein will be used in sensitive cell culture systems.
Additional best practices:
Avoid repeated freeze-thaw cycles, as these can reduce protein activity.
If using for functional assays, confirm the activity of the reconstituted protein with a small-scale pilot experiment.
If the protein is sensitive to oxidation or aggregation, consider adding reducing agents or glycerol (5–50%) for enhanced stability during storage.
Summary table:
Step
Details
Reconstitution
0.1–1.0 mg/mL in sterile water or PBS
Carrier protein
0.1% BSA, 10% FBS, or 5% HSA recommended for cell culture applications
Aliquoting
Yes, to avoid freeze-thaw cycles
Storage
−20°C to −80°C (long-term), 4–8°C (short-term, ≤7 days)
Handling
Gentle mixing, avoid vigorous agitation
These steps will help ensure the activity and stability of recombinant ALK-2 for cell culture experiments. Always consult the specific product datasheet for any additional recommendations.
Products are for research use only. Not for use in diagnostic or therapeutic procedures.
