Recombinant Human Androgen Receptor Protein: Protocol Guide

Recombinant Human Androgen Receptor Protein is a purified nuclear receptor protein widely used in ligand-binding assays, transcriptional activity studies, and drug discovery research targeting androgen signaling pathways.

Protein Name

Recombinant Human Androgen Receptor (AR) Protein

SKU

rp366424

Protein Family

Nuclear receptor superfamily (NR3C4)

Recommended Storage

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

Key Applications

Ligand-binding assays, EMSA, co-immunoprecipitation, transcription factor studies, drug screening

Host Expression System

Refer to product datasheet for confirmed expression host details

Materials and Equipment Required

Before beginning the protocol, ensure the following materials are available:

• Recombinant Human Androgen Receptor Protein (SKU: rp366424)
• Sterile, nuclease-free water or recommended reconstitution buffer (typically PBS or Tris-HCl buffer, pH 7.4–8.0, with carrier protein such as 0.1% BSA)
• Microcentrifuge tubes (low-binding, 1.5 mL)
• Ice bucket and wet ice
• Calibrated micropipettes and sterile tips
• Spectrophotometer or fluorometer (for protein quantification if required)
• SDS-PAGE and Western blot equipment (for QC validation)
• Ligand of interest (e.g., dihydrotestosterone, DHT) dissolved in DMSO or ethanol at appropriate stock concentration
• Assay-specific reagents (e.g., labeled ligand for competitive binding assay, luciferase reporter system for transcriptional assays)

Note: Always consult the product-specific datasheet supplied with SKU rp366424 for confirmed buffer compositions and protein concentrations prior to use.

Reconstitution and Storage Protocol

Proper reconstitution and storage are critical to maintaining the biological activity of the Recombinant Human Androgen Receptor Protein.

Step 1: Thawing

Transfer the vial from -80 °C to ice and allow it to thaw slowly on ice (approximately 10–15 minutes). Do not thaw at room temperature or by warming in hands, as rapid temperature changes may denature the protein.

Step 2: Brief Centrifugation

Briefly centrifuge the vial (300–500 × g, 30 seconds) to collect any condensate from the lid and walls before opening.

Step 3: Reconstitution (lyophilized form, if applicable)

If the product is supplied in lyophilized form, reconstitute by adding the volume of sterile reconstitution buffer specified on the datasheet directly to the vial. Gently pipette up and down; do not vortex. Allow the solution to stand on ice for 5 minutes to ensure complete dissolution.

Step 4: Aliquoting

Prepare single-use aliquots to avoid repeated freeze-thaw cycles, which degrade protein activity. Store aliquots at -80 °C.

Step 5: Short-Term Storage

For use within 1–2 weeks, aliquots may be stored at 4 °C. For long-term storage, maintain at -80 °C. Refer to the product datasheet for specific stability data.

Important: Adding a carrier protein (0.1% BSA) to the working solution can help prevent adsorption losses, particularly at low protein concentrations.

Androgen Receptor Ligand-Binding Assay Protocol

The ligand-binding assay is a primary application for Recombinant Human AR Protein and is used to assess the affinity of ligands (agonists, antagonists, or candidate drug molecules) for the AR ligand-binding domain (LBD).

Assay Setup

1. Prepare the AR protein working solution at the concentration specified in your assay protocol (typically in the nanomolar range; consult the datasheet for recommended concentrations).
2. Prepare serial dilutions of the test ligand and a reference competitor (e.g., unlabeled DHT) in assay buffer.
3. Combine AR protein, labeled tracer ligand (e.g., fluorescently or radioactively labeled DHT), and test compounds in assay tubes or microplate wells. Bring the total assay volume to the desired amount with assay buffer.
4. Incubate at the temperature and duration specified by your assay format (commonly 4 °C for 2–18 hours or room temperature for shorter incubations), protected from light if using fluorescent tracers.

Separation and Detection

1. Separate bound from free ligand using the method appropriate to your assay format (e.g., size-exclusion spin columns, charcoal-dextran method, or TR-FRET detection without separation).
2. Measure signal according to the detection modality (e.g., fluorescence, radioactivity, luminescence).
3. Calculate percent inhibition, IC50, or Ki values using appropriate curve-fitting software.

Tip: Include non-specific binding controls (excess unlabeled ligand) and total binding controls in every experiment to ensure assay validity.

Quality Control and Troubleshooting

Validating the integrity and activity of the Recombinant Human Androgen Receptor Protein before downstream experiments is essential for reproducible results.

Quality Control Checks

• SDS-PAGE / Western Blot: Confirm the expected molecular weight of the AR protein (full-length human AR is approximately 98–110 kDa; tag or truncated forms may differ — confirm on datasheet). Use an anti-AR or anti-tag antibody for Western blot verification.
• Protein Concentration: Verify protein concentration using a Bradford or BCA assay if required by your downstream application.
• Activity Confirmation: Where possible, confirm ligand-binding activity using a known high-affinity ligand (e.g., DHT, Kd ~0.1–1 nM) as a positive control.

Troubleshooting

Problem	Possible Cause	Suggested Action
Low or no binding signal	Protein denatured or inactive	Check freeze-thaw history; use fresh aliquot; verify storage temperature
High background / non-specific signal	Insufficient blocking or ligand concentration too high	Optimize ligand and protein concentrations; increase wash stringency
Protein precipitation	Incompatible buffer or incorrect pH	Reconstitute in recommended buffer; verify pH; add BSA carrier
Inconsistent results between replicates	Pipetting error or protein adsorption to tubes	Use low-binding tubes; pre-coat with BSA; vortex gently before use

Downstream Applications and Research Context

The Androgen Receptor (AR, gene NR3C4) is a ligand-activated transcription factor belonging to the nuclear receptor superfamily. Upon binding androgens such as testosterone or dihydrotestosterone (DHT), AR translocates to the nucleus, dimerizes, and binds to androgen response elements (AREs) in the promoters of target genes to regulate transcription.

Recombinant Human Androgen Receptor Protein (SKU: rp366424) supports a broad range of research applications:

• Drug Discovery & Screening: Identification and characterization of AR agonists, antagonists, and selective androgen receptor modulators (SARMs) relevant to prostate cancer, male hypogonadism, and muscle-wasting diseases.
• Structural Biology: Protein–ligand co-crystallization and cryo-EM studies of AR conformational states.
• Biochemical Assays: Electrophoretic mobility shift assays (EMSA) to study AR–DNA interactions; co-immunoprecipitation (Co-IP) to map coactivator/corepressor interactions.
• Transcriptional Reporter Assays: Use in cell-free or cell-based transcription systems to evaluate ARE-driven gene expression.
• Endocrine Disruption Research: Assessment of environmental compounds for androgenic or anti-androgenic activity.

AR dysregulation is implicated in prostate cancer, androgen insensitivity syndrome (AIS), polycystic ovary syndrome (PCOS), and other endocrine disorders, making this protein a high-value research tool across oncology, endocrinology, and pharmacology disciplines.

Frequently asked questions

How should I reconstitute the Recombinant Human Androgen Receptor Protein?

If the protein is supplied in lyophilized form, reconstitute it by adding the volume of sterile buffer recommended on the product datasheet (typically PBS or Tris-HCl, pH 7.4–8.0, with 0.1% BSA) directly to the vial. Gently pipette to mix — do not vortex — and allow to stand on ice for 5 minutes. Always consult the specific datasheet for SKU rp366424 for confirmed reconstitution instructions.

What are the recommended storage conditions to preserve AR protein activity?

Store the Recombinant Human Androgen Receptor Protein at -80 °C for long-term preservation. Prepare single-use aliquots to avoid repeated freeze-thaw cycles, which progressively reduce protein activity. For short-term use within 1–2 weeks, aliquots may be stored at 4 °C. Adding a carrier protein such as 0.1% BSA to the working solution helps prevent adsorption losses at low concentrations.

What positive control should I use to validate AR ligand-binding activity?

Dihydrotestosterone (DHT) is the most commonly used positive control for AR ligand-binding assays due to its high affinity for the AR ligand-binding domain. Use a concentration series around the expected Kd to generate a competition curve and confirm assay performance. Including both total binding and non-specific binding controls in every experiment is essential for data quality.

Can this protein be used in cell-based transcriptional reporter assays?

Recombinant Human Androgen Receptor Protein can support cell-free transcription systems, and exogenous AR protein is also widely used in research workflows where AR expression is supplemented or studied in specific cellular contexts. For cell-based ARE-luciferase reporter assays, an AR expression vector or purified protein introduced via transfection or direct addition may be used depending on the assay design. Consult the literature and the product datasheet for validated application conditions.

What troubleshooting steps should I take if I observe high background in a ligand-binding assay?

High background is often caused by excess free labeled ligand, insufficient wash steps, or non-specific binding of the tracer to assay vessels. To troubleshoot: optimize the concentration of labeled tracer (use the minimum effective concentration), increase the number or stringency of wash steps, use low-binding assay plates or tubes, and include appropriate non-specific binding controls with saturating concentrations of unlabeled competitor ligand.

References

1. Heinlein CA, Chang C. Androgen receptor in prostate cancer. Endocr Rev. 2004;25(2):276-308. doi:10.1210/er.2002-0032
2. Mangelsdorf DJ, et al. The nuclear receptor superfamily: the second decade. Cell. 1995;83(6):835-839. doi:10.1016/0092-8674(95)90199-x
3. Bain DL, et al. Androgen receptor structure, function and biology: from bench to bedside. Clin Sci (Lond). 2007;110(2):191-207. doi:10.1042/CS20050357

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