As a core member of the small GTPase family, the G12V mutation in KRAS leads to the loss of endogenous GTP hydrolysis activity, locking the protein in a persistently activated conformation and driving constitutive activation of downstream signaling pathways. Due to the lack of classic hydrophobic pockets suitable for small molecule binding on the KRAS protein surface, traditional inhibitor development targeting this protein has long faced bottlenecks. The emergence of proteolysis-targeting chimera (PROTAC) technology provides an alternative solution to this challenge. This technology utilizes heterobifunctional molecules that simultaneously bind to the target protein and E3 ubiquitin ligase, inducing polyubiquitination modification of the target protein and its degradation via the proteasome pathway. In this process, evaluating the formation efficiency of ternary complexes among the target protein, E3 ligase, and degrader molecules is a core step in screening and optimizing candidate molecules. Establishing a sensitive, reliable, and high-throughput-compatible binding assay is of significant research importance.
Time-resolved fluorescence resonance energy transfer (TR-FRET) is a homogeneous detection technology whose core lies in utilizing the unique fluorescence properties of lanthanide chelates to achieve precise quantitative analysis of molecular interactions. Lanthanide elements exhibit long fluorescence lifetimes ranging from microseconds to milliseconds, compared to the nanosecond-level background fluorescence commonly present in biological samples. By setting appropriate time-delayed gating for signal acquisition, nonspecific fluorescence interference can be effectively eliminated, significantly improving the signal-to-noise ratio.
In the KRAS and CRBN binding assay system, donor fluorophore-labeled KRAS G12V protein and acceptor fluorophore-labeled CRBN protein are brought into proximity under the bridging of a targeted protein degrader molecule. When the donor is excited by light of a specific wavelength, if the spatial distance between the two is less than ten nanometers, energy is transferred to the acceptor molecule via non-radiative dipole resonance, causing it to emit fluorescence at a characteristic wavelength. The intensity of this signal is positively correlated with the number of ternary complexes formed, enabling quantitative assessment of binding efficiency.
The core components of the detection system include recombinant KRAS G12V protein, CRBN-DDB1 complex, and corresponding fluorescent labeling reagents. The donor fluorophore uses a europium chelate-labeled anti-tag antibody with an excitation wavelength of approximately 340 nm and an emission wavelength of 620 nm. The acceptor uses a streptavidin-conjugated fluorophore with an excitation wavelength of 620 nm and an emission wavelength of 665 nm.
The system employs an indirect labeling strategy. Biotinylated KRAS G12V protein is conjugated to the acceptor fluorophore via high-affinity streptavidin-biotin interaction. CRBN protein with a specific affinity tag is fluorescently labeled through specific recognition by the donor antibody. When the targeted protein degrader molecule is added to the system, its two ligands bind to KRAS G12V and CRBN, respectively, bringing the two fluorescently labeled proteins into proximity and generating detectable TR-FRET signals. The system adopts a homogeneous design, with all reaction steps completed sequentially in the same well, eliminating the need for separation or washing steps, making it inherently suitable for high-throughput screening in 96- or 384-well microplates.
Before detection, all frozen components should be equilibrated to room temperature, avoiding repeated freeze-thaw cycles. First, add KRAS G12V and CRBN protein working solutions diluted in assay buffer to each well of the microplate. Then add serially diluted test PROTAC compounds, with negative control wells receiving buffer instead of compound solution. The reaction mixture is incubated at room temperature in the dark for 90-120 minutes to ensure binding equilibrium is reached.
After incubation, add pre-mixed donor and acceptor fluorescent labeling reagents to each well and continue incubation at room temperature in the dark for 30-60 minutes. Use a microplate reader equipped with time-resolved fluorescence detection to collect dual-wavelength signals, recording fluorescence intensities at 620 nm and 665 nm. To correct for well-to-well volume variations and pipetting errors, final results are presented as the ratio of 665 nm to 620 nm signals.
The dose-response relationship between TR-FRET signal ratio and PROTAC concentration follows a classic four-parameter logistic equation model. Nonlinear regression fitting of experimental data yields the half-maximal effective concentration (EC50) characterizing binding efficiency and the ceiling effect value reflecting maximum binding capacity. Experimental design must include positive control compounds with known activity to validate the system's response sensitivity and stability in each run.
Special attention should be paid to potential hook effects at high concentrations. This phenomenon occurs when excessive PROTAC molecules favor the formation of nonproductive binary complexes (target protein-degrader or E3 ligase-degrader) rather than the intended ternary complex. Additionally, the window coefficient (Z') is a key metric for evaluating assay robustness and screening suitability, typically requiring a value greater than 0.5 for large-scale high-throughput screening. Reproducibility validation data show that this method has intra-assay coefficients of variation below 10% and inter-assay coefficients below 15%.
Nanjing UA-Bio Technology Co., Ltd. (UA-Bio) has independently developed the "UniOne® TR-FRET Human KRAS[G12V]/CRBN PROTAC Binding Kit (GDP/GTP load)" (Catalog No.: UA086003), a high-performance analysis platform specifically designed for studying PROTAC molecules targeting KRAS G12V mutant protein-induced interactions between KRAS G12V and CRBN (Cereblon) E3 ubiquitin ligase. This kit is based on time-resolved fluorescence resonance energy transfer (TR-FRET) technology and supports evaluation of PROTAC-mediated ternary complex formation activity between KRAS G12V and CRBN under GDP- or GTP-loaded states, providing stable and reliable standardized solutions for targeted protein degradation (PROTAC) technology development, antitumor drug screening, and mutation-specific degrader research.
| Core Product Advantages | Detailed Parameters / Functional Description |
|---|---|
| High Purity and Intact Biological Activity | The kit's core components use highly purified, biologically active human KRAS G12V mutant protein (supporting GDP or GTP loading states) and CRBN-DDB1 complex, validated through multidimensional quality control. The KRAS G12V protein maintains correct native conformation and nucleotide-binding states, accurately simulating PROTAC-mediated specific ternary complex formation under physiological conditions, ensuring data accuracy, reproducibility, and functional relevance. |
| Excellent Batch-to-Batch Consistency and Stability | Relying on internationally leading protein expression platforms and highly standardized production processes, combined with stringent quality control systems, the product exhibits excellent long-term stability and exceptional batch-to-batch consistency, providing solid quality assurance for long-term, continuous PROTAC drug screening and mechanism research. |
| Ready-to-Use Flexible Experimental Platform | Based on homogeneous TR-FRET technology, the kit adopts a simple "add-incubate-read" operation mode without cumbersome washing steps. Its optimized formulation is compatible with multi-well plate (96/384-well) automation platforms, flexibly applicable to high-throughput screening of KRAS G12V-targeting PROTAC molecules, nucleotide state-dependent degrader evaluation, ternary complex formation assays, and competitive binding experiments. |
| Complete Solutions and Professional Support | We provide fully validated standard protocols, typical dose-response curves, and detailed result interpretation guidelines to help quickly establish stable, reproducible experimental workflows. Nanjing UA-Bio's professional team offers comprehensive technical consultation and support for research design, experimental optimization, and data analysis. |
Nanjing UA-Bio Technology Co., Ltd. remains committed to providing cutting-edge, high-quality core reagents and tools for immunology, cell therapy, and innovative drug development. For detailed technical parameters, validation data, or specific application inquiries regarding the "UniOne® TR-FRET Human KRAS[G12V]/CRBN PROTAC Binding Kit (GDP/GTP load)" (Catalog No.: UA086003), please feel free to contact us.
