GST Pull Down Assay Service

MtoZ Biolabs provides GST Pull Down Assay Service to investigate protein binding using GST-tagged bait proteins and identify candidate binding partners through high-resolution LC-MS/MS analysis.

From protein capture to mass spectrometry-based identification, our service supports candidate binding protein screening, follow-up of Co-IP findings, and protein-level result comparisons.

GST-tagged bait protein-based interaction studies
High-resolution Orbitrap LC-MS/MS analysis
Protein identification and relative abundance comparison

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What Is GST Pull-Down?

GST Pull-Down uses a GST-tagged bait protein to capture candidate binding partners through the affinity between GST and glutathione immobilized on a suitable support. After incubation with a compatible protein sample, the captured material is recovered for downstream analysis.

The method is useful for investigating interactions between defined proteins and identifying candidate proteins from a complex mixture. When coupled with LC-MS/MS, GST pull-down samples can be analyzed to identify proteins and evaluate their relative abundance when the experimental design and data support such comparisons.

When GST Pull-Down Is a Good Fit

GST Pull-Down is suitable for projects in which a GST-tagged bait protein is available and the research objective involves one or more of the following:

1. Investigating Candidate Protein Binding

Assess whether a candidate protein is associated with a GST-tagged bait in a defined in vitro system.

2. Identifying Unknown Binding Partners

Use LC-MS/MS to identify proteins recovered from a GST pull-down sample.

3. Following up on Co-IP Findings

Examine candidate interactions using an in vitro approach that differs from cellular immunoprecipitation.

4. Comparing Experimental Conditions

Evaluate differences in identified proteins or relative abundance when suitable comparison groups and controls are included.

GST Pull-Down vs. Pull-Down Assay: How to Choose?

GST Pull-Down is a specific type of Pull-Down assay that uses a GST-tagged bait protein for affinity capture. The choice between GST Pull-Down and a broader Pull-Down approach depends primarily on the bait protein format, affinity tag, and research objective.

Comparison	GST Pull-Down Assay	Pull-Down Assay
Bait protein	GST-tagged bait protein	Bait proteins using different compatible affinity tags or capture strategies
Best suited for	Projects using an established GST-tagged bait to investigate candidate protein interactions	Projects requiring a broader assessment of suitable bait formats or affinity-based capture strategies
Method selection	Uses GST–glutathione affinity for bait capture	Depends on the bait tag, capture chemistry, and experimental requirements
Key consideration	GST-tag integrity, bait protein quality, and potential tag-associated background	Compatibility between the bait protein, affinity system, and target interaction
Service selection	Choose when a GST-tagged bait is available and suitable for the study	Choose when another tag is available or the appropriate Pull-Down strategy needs to be assessed

How to choose: If your bait protein is already GST-tagged, GST Pull-Down is a direct option for your interaction study. If your bait uses another affinity tag or you are still determining the appropriate capture strategy, MtoZ Biolabs can assess your project requirements and recommend a suitable Pull-Down approach.

Both GST Pull-Down and broader Pull-Down assay services are available from MtoZ Biolabs. Share your bait protein information, sample type, and research objective to help determine the appropriate experimental workflow.

Service at MtoZ Biolabs

MtoZ Biolabs provides GST Pull-Down-related protein interaction analysis with a focus on protein identification by high-resolution LC-MS/MS. The appropriate workflow depends on whether the project involves an established pull-down sample or material requiring further assessment.

1. GST Pull-Down Sample Analysis

Proteomic identification of proteins in submitted GST pull-down material.

2. Candidate Binding Partner Identification

Identification of proteins recovered from the pull-down experiment using database searching.

3. Relative Abundance Comparison

Comparison of protein abundance across submitted experimental groups when sample design and data quality support the analysis.

4. Project-Specific Assessment

Review of the bait protein, sample type, buffer composition, protein amount, and reference database before analysis.

The execution scope of the upstream GST capture experiment should be confirmed during project assessment when the customer requires the complete pull-down assay rather than downstream mass spectrometry analysis alone.

Analysis Workflow

1. Project and Sample Assessment

Review the research objective, sample format, protein amount, buffer composition, and reference database.

2. Reduction and Alkylation

Prepare proteins for enzymatic digestion.

3. Trypsin Digestion

Digest proteins into peptides for LC-MS/MS analysis.

4. C18 Desalting

Remove interfering components before peptide separation and mass spectrometry.

5. Nano-LC-MS/MS Analysis

Separate peptides by nano-liquid chromatography and analyze them using high-resolution Orbitrap-series mass spectrometry.

6. Database Searching

Search the acquired data using MaxQuant and an appropriate UniProt or customer-provided reference database.

7. Data Reporting

Compile protein identification results, peptide information, sequence coverage, scores, intensity information, and the PDF report.

Data-dependent acquisition (DDA) is the primary acquisition mode. Data-independent acquisition (DIA) can be considered upon request, subject to project requirements and technical feasibility.

Figure 1. Schematic Outline of the GST Pull-Down Assay Pipeline

Experimental Instruments

GST Pull-Down sample analysis is performed using an Orbitrap-series high-resolution mass spectrometry platform coupled with nano-liquid chromatography.

Mass spectrometry platform: Orbitrap-series high-resolution mass spectrometry.
Mass accuracy: Less than 5 ppm.
Data processing: MaxQuant.
Reference database: UniProt or a customer-provided protein database.

Sample Submission Suggestions

Sample type	Submission requirements	Storage and transport
Gel bands	Protein bands should be visible to the naked eye.	Ship at room temperature or with an ice pack.
Protein solution or eluate	Recommended total protein amount: at least 20 μg; concentration above 0.5 μg/μL.	Snap-freeze in liquid nitrogen and ship on dry ice.
Pull-Down or IP magnetic beads	Confirm the sample amount and buffer composition before submission.	Snap-freeze in liquid nitrogen and ship on dry ice.
Other biological materials	Original animal or plant tissues, cells, microorganisms, or body fluids may be considered after project assessment.	Confirm the sample format and handling requirements before shipment.

For samples that do not meet the recommended input requirements, contact the team before shipment to assess feasibility.

Advantages of GST Pull-Down Assay Service

1. In Vitro Interaction Assessment

GST-tagged bait proteins support the investigation of candidate binding partners under defined experimental conditions, complementing interaction studies performed in cellular systems.

2. Mass Spectrometry-Based Protein Identification

High-resolution LC-MS/MS and database searching support the identification of proteins recovered from pull-down samples, extending the analysis beyond a predefined list of candidate proteins.

3. Structured Protein-Level Reporting

Results include protein and peptide identification information, sequence coverage, identification scores, and intensity values to support review of the detected proteins.

4. Project-Specific Analysis Planning

Sample format, input amount, buffer composition, reference database, and comparison requirements are reviewed to align the analysis with the research objective.

5. One-Time Charge

Our pricing is transparent, with no hidden fees or additional costs.

Deliverables

1. Raw Mass Spectrometry Files

Original files generated during LC-MS/MS data acquisition.

2. Protein Identification Results

An Excel file containing identified proteins, peptide information, sequence coverage, identification scores, and intensity values.

3. Relative Abundance Information

Intensity-based information for comparing samples when supported by the experimental design and data.

4. PDF Report

A consolidated report of the analysis results.

The final reporting scope depends on the agreed project design and the quality and completeness of the submitted samples and reference database.

FAQ

1. Can GST Pull-Down-MS identify previously unknown binding partners?

Yes. LC-MS/MS can identify proteins recovered from a GST pull-down sample, including candidate binding partners that were not specified before the experiment. Identification results should be interpreted alongside the control groups, background binding, and experimental design.

2. Why is a GST-only control important?

GST itself or the affinity support may contribute to nonspecific protein adsorption. A GST-only control, where appropriate to the experimental design, can help distinguish proteins associated with the GST tag or capture system from proteins enriched in the presence of the bait fusion protein.

3. Does a GST Pull-Down result prove that two proteins interact inside cells?

No. GST Pull-Down evaluates binding under in vitro conditions. A positive result supports an association under the tested conditions but does not establish that the interaction occurs in cells or that the interaction is physiologically relevant. Additional evidence may be needed to address those questions.

4. Can samples be submitted if the GST Pull-Down experiment has already been completed?

Yes. Compatible completed pull-down materials, including gel bands, eluates, and bead-bound samples, may be considered for downstream analysis. Sample amount, buffer composition, and handling requirements should be confirmed before shipment.

5. What information is needed for a project assessment?

Provide the bait protein identity, sample type, available protein amount, buffer composition, experimental and control groups, research objective, and reference database when available. These details help determine sample compatibility and the appropriate protein identification workflow.

Start Your Project with MtoZ Biolabs

Planning a GST Pull-Down project? Share the bait protein identity, sample format, available protein amount, buffer composition, and research objective with MtoZ Biolabs. The team can review the sample requirements and clarify whether your project requires downstream LC-MS/MS identification or a broader pull-down workflow.