Natural products often exhibit complex polypharmacology, interacting with multiple proteins within a cellular environment. Traditional methods for target identification frequently suffer from high false-positive rates and a lack of quantitative precision. To address these limitations, we utilize ABPP coupled with stable isotope labeling by amino acids in cell culture (SILAC), a quantitative chemoproteomic strategy designed to map the protein targets of bioactive molecules with unprecedented accuracy. By combining the functional labeling of ABPP with the metabolic encoding of SILAC, we provide a "gold standard" service for pharmaceutical and academic researchers.
What is ABPP Coupled with SILAC Technique?
ABPP coupled with SILAC (ABPP–SILAC) is a quantitative proteomic approach used to identify the direct protein targets of small molecules (such as drugs or natural products) in a native biological context.
- ABPP utilizes chemical probes that react with the active sites of specific protein families, allowing researchers to monitor protein function rather than just abundance.
- SILAC is a mass spectrometry (MS)-based quantitative technique that uses "light" and "heavy" stable isotopes to label cell populations, enabling the precise comparison of protein levels between different samples.
By merging these two, we can quantitatively measure the competition between a natural product and a chemical probe, effectively filtering out non-specific binders and identifying the true "hits."
Principle of the Technique
Typically, the fundamental principle of ABPP–SILAC centers on a competitive binding assay performed within a quantitatively controlled proteomic environment. Initially, two separate cell populations are metabolically engineered via SILAC, where one group is cultured in media containing "light" amino acids (natural isotopes) and the other in "heavy" media (stable isotopes like 13C or 15N). Following full isotope incorporation, the "heavy" group is pre-treated with the bioactive natural product of interest to occupy its specific protein binding sites, while the "light" group remains untreated as a control. An activity-based probe (ABP), designed to covalently react with active-site residues, is then introduced to both groups; however, the probe can only label proteins whose active sites have not been blocked by the natural product. When the lysates are combined and analyzed by high-resolution mass spectrometry, most proteins will appear as 1:1 peptide pairs, indicating no competition. Conversely, a significantly diminished intensity in the "heavy" peptide peak relative to the "light" peak—resulting in a high L/H ratio—provides a definitive quantitative readout that the natural product has successfully outcompeted the probe for that specific protein target.
Fig. 1. Principle of ABPP–SILAC.
Our ABPP–SILAC Technology Platform
We have established an advanced ABPP–SILAC technology platform tailored specifically for the challenges of bioactive natural product research.
Key Capacities of Our Platform
- Custom-designed activity-based probes
- Optimized SILAC-compatible cell culture systems
- Competitive and non-competitive ABPP strategies
- High-resolution LC–MS/MS proteomics
- Robust bioinformatics and quantitative data analysis pipelines
Our platform supports diverse biological models, including cancer, inflammation, metabolic, and neurological disease-related cell systems. Importantly, we offer flexible experimental designs, including cell lysate-based profiling and live-cell competitive ABPP–SILAC, ensuring physiological relevance and broad applicability.
Typical Workflow of ABPP–SILAC
Step 1
Cell Culture & SILAC Labeling
Cells are cultured for 5–6 doublings in "light" and "heavy" media to ensure complete replacement of endogenous amino acids.
Step 2
Compound Treatment
The "heavy" cell lysate (or live cells) is incubated with the natural active component. The "light" group is treated with a vehicle control (e.g., DMSO).
Step 3
Probe Incubation
A specialized ABP (biotinylated or "click-chemistry" compatible) is added to both samples to label available active sites.
Step 4
Sample Mixing & Enrichment
The "light" and "heavy" samples are combined in a 1:1 ratio. Labeled proteins are enriched using streptavidin beads.
Step 5
Tryptic Digestion & LC-MS/MS
Proteins are digested into peptides and analyzed via liquid chromatography-tandem mass spectrometry.
Step 6
Data Analysis
We measure the ratio of "light" vs. "heavy" peptide pairs. A significant decrease in the Heavy peak intensity identifies the protein as a target of the natural product.
Key Advantages of ABPP–SILAC
- Exceptional Quantitative Accuracy: SILAC minimizes "noise" and experimental error because the samples are mixed early in the process and processed as a single tube.
- Functional Insights: Unlike standard proteomics, ABPP specifically tracks the active state of proteins, providing information on the functional impact of the natural product.
- Native Environment: The binding occurs in the presence of all cellular cofactors and post-translational modifications, reflecting the true biological interaction.
- Elimination of False Positives: Non-specific "background" proteins will show a 1:1 ratio (Light:Heavy), allowing us to easily discard them and focus only on proteins showing true competition.
- High Sensitivity: We can identify low-abundance targets that might be missed by less sensitive staining or labeling methods.
ABPP–SILAC combines chemical biology with quantitative proteomics, enabling highly accurate, system-wide identification of functional protein targets directly in complex biological environments. Through our ABPP–SILAC technology platform, we empower researchers to uncover the true molecular targets of bioactive natural products, accelerating drug discovery from nature to clinic.
Online Inquiry
Frequently Asked Questions (FAQ)
Q1: Can this technique be used for live-cell target identification?
Q2: How do you choose the right probe?
A: We select probes based on the chemical structure of your natural product or the suspected protein family it targets (e.g., kinases, proteases, or hydrolases). We also offer "universal" probes for broader screening.