Transcreener® GDP GTPase Assay Kits

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GTPase Assay Kits for Direct GDP Detection

Transcreener® GDP Assay

Measure GTP hydrolysis by directly quantifying GDP formation with a homogeneous, mix-and-read biochemical assay. Transcreener GDP GTPase Assay Kits are designed for purified GTPases, GAPs, and GEFs and are available in FP, FI, and TR-FRET formats for 96-, 384-, and 1536-well applications.

Sensitive at low enzyme turnover by detecting GDP formation instead of GTP depletion
Universal detection for GTPases and GDP-producing enzyme reactions
Far-red FP, FI, and TR-FRET readouts to reduce compound interference
HTS-ready, mix-and-read workflow with no coupling enzymes

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Overview – Transcreener GDP GTPase Assay Kits

What Does This GTPase Assay Measure?

GTPase assays can measure either catalytic GTP hydrolysis or the amount of active, GTP-bound protein in a biological sample. The Transcreener GDP Assay is an in vitro biochemical activity assay that directly measures GDP produced as purified GTPases hydrolyze GTP.

Because it measures reaction product rather than depletion of an abundant GTP substrate, Transcreener is particularly useful for slow-turnover GTPases and low-conversion assay conditions. It does not require modified nucleotides, radioactive substrates, or coupling enzymes.

This assay is intended for purified enzyme systems. It is not a cell-based GTPase activation or pull-down assay.

GTPase Enzyme Reaction Cycle

The kit directly measures GDP produced by GTPase reactions as they hydrolyze GTP, giving you a fast, universal way to quantify enzyme activity in real time. Ideal for quick and simple high-throughput screening of GTPases, along with GAPs and GEFs. The generic nature of the assay simplifies compound and inhibitor profiling for multiple GTPase targets.

Learn More About Measuring GEF and GAP Activity:

A GTPase Activity Assay Kit with Direct GDP Readout

Transcreener GDP GTPase Assay Kits monitor enzyme turnover by directly measuring GDP formation during GTP hydrolysis. This direct-detection GTPase assay delivers strong signal even at low conversion, supports FP, FI, and TR-FRET formats, and avoids phosphate-background issues common in older GTP depletion assays.

If you’re looking for a universal, HTS-ready GTPase activity assay kit, this platform provides a simple and reliable GDP readout across targets.

How Does The GTPase Assay Work?

The Transcreener GDP Assay measures GTPase enzyme activity by directly measuring the GDP produced during GTP hydrolysis. By detecting GDP output, the assay provides a universal method to assess the activity of any GDP-producing enzyme in real-time.

Transcreener GTPase technology uses a simple but highly effective method that consists of an antibody selective to GDP and a far-red fluorescent tracer. GDP produced in the reaction competes with the tracer changing the fluorescent properties and providing fluorescent readout.

The GTPase assay kit is available with FP, FI, and TR-FRET. It is a simple mix-and-read format. Perform your enzyme reaction, add the detection reagent, and measure. The simplicity of the system yields robust results that also make it an excellent fit for HTS.

Advantages of GDP Detection Over GTP Depletion Assays for GTPase Discovery

Exciting new strategies for inhibiting GTPases in the Ras and Rho families have emerged over the last several years. This video walks through how the Transcreener GDP GTPase Assay can help researchers unlock novel GTPase inhibitors and outlines the advantages of GDP detection over GTP depletion assay strategies.

Far Red FP, FI &TR-FRET Readouts Validated on Major Multimode Readers

Profiling GTPase Inhibitors for Effects on GTP Hydrolysis for Rho and Ras GTPases

Specifications

What’s Included

FP
	1K		10K
Component	Part #	Qty	Part #	Qty
GDP Alexa633 Tracer, 400 nM	2043	100 µL	2047	1 mL
GDP Antibody, 3.2 mg/mL	2044	350 µL	2048	3.3 mL
Stop & Detect Buffer B, 10X	2027	1 mL	2032	10 mL
5 mM GDP	2045	200 µL	2049	2 mL
5 mM GTP	2046	200 µL	2050	2 mL

FI
	1K		10K
Component	Part #	Qty	Part #	Qty
GDP Alexa594 Tracer, 800 nM	2081	100 µL	2083	1 mL
GDP Antibody-IRDye® QC-1, 1.4 mg/mL	2082	670 µL	2084	2 x 3.35 mL
Stop & Detect Buffer B, 10X	2027	1 mL	2032	10 mL
5 mM GDP	2045	200 µL	2049	2 mL
5 mM GTP	2046	200 µL	2050	2 mL

TR-FRET
	1K		10K
Component	Part #	Qty	Part #	Qty
GDP Hilyte647 Tracer, 10 µM	2161	200 µL	2163	2 x 1 mL
GDP Antibody-Tb, 800 nM	2162	100 µL	2164	1 mL
Stop & Detect Buffer C, 10X	2062	1 mL	2065	10 mL
5 mM GDP	2045	200 µL	2049	2 mL
5 mM GTP	2046	200 µL	2050	2 mL

What You Will Need

Component	Notes
GTPase Enzyme	Please use purified enzymes for the best results.
Enzyme Buffer	User-supplied enzyme buffer components include enzyme, buffer, acceptor substrate, MgCl₂ or MnCl₂, Brij-35, and test compounds.
Assay Plates	Assay Plates Can Be Purchased Separately From BellBrook Labs. FP - An entirely black plate with a non-binding surface is required. We suggest Corning 384-well plates (Cat. #4514) or 1536-well plates (Cat. #3728). FI - An entirely black plate with a non-binding surface is required. We suggest Corning 384-well plates (Cat. #4514), Corning 96-well, half-area plates (Cat. # 3686) or 1536-well plates (Cat. #3728). TR-FRET - An entirely white plate with a non-binding surface is required. We suggest Corning 384-well plates (Cat. #4513) or 1536-well plates (Cat. #3729).
Plate Reader	A multi-detection microplate reader configured to measure output of the GDP tracer is required.
Liquid Handling Devices	Use liquid handling devices that can accurately dispense a minimum volume of 0.5 µL into 384-well plates.
Ultrapure Water	Some deionized water systems are contaminated with nucleases that can degrade both nucleotide substances and products, reducing assay performance. Careful handling and use of ultrapure water eliminates this potential problem.

Use with a Variety of GTPase Enzymes

Based on BellBrook Lab’s proprietary nucleotide immunodetection technology, the Transcreener GDP Assays are compatible with any enzyme class that produces GDP. This includes monomeric small G proteins, such as CDC42, and Gα subunits of heterotrimeric G proteins, such as Gαi1.

Learn how Transcreener can be used to study targets like Cdc42 and RhoA in Springer’s Rho GTPases Methods and Protocols. Discover how researchers at UT Southwestern used the GDP assay to screen dynamin GTPase activity.

GTPase Enzyme Titration with Cdc42 and RhoA

Cdc42 and RhoA GTPase titration using the Transcreener GDP Assay with an FP readout

Example Targets

Click on the respective target to learn more.

GTPase Family	Enzyme	Enzyme Type
Ras Family	KRas	Wild Type
	KRas G12C	Mutant
	KRas G12D	Mutant
	KRas G12V	Mutant
	HRas	Wild Type
	HRas G12C	Mutant
	NRas	Wild Type
	NRas G12C	Mutant
	RRas	Wild Type
Rho Family	RhoA	Wild Type
	RhoC	Wild Type
	Cdc42	Wild Type
	Rac1	Wild Type
Rab Family	Rab2	Wild Type

Applications

Measure enzymatic activity of GTPase
Screen compound libraries for GTPase Modulators
Quantify Inhibitor Potency
Inhibitor Selectivity Profiling
Measure Drug-Target Residence Time

Features

Direct detection of GDP to monitor GTPase, GAP, and GEF activity
Easy to use, homogenous, one-step format
Far-red fluorescent readouts minimize compound interference
A safe, non-radioactive method (no disposal concerns)
Stable assay reagents- minimum 8-hour reagent and signal stability even at room temperature!
More sensitive and less subject to interference than colorimetric phosphate detection methods such as malachite green

What Can You Do With Transcreener

Measure guanine nucleotide exchange factor (GEF) activity
Measure GTPase-activating proteins (GAP) activity
Detect any GDP producing enzyme: GTPases, Gα proteins, Ras-like G proteins (Ras, Roc, Rac, cdc42, etc.), fucosyltransferases, mannosyltransferases

Easy-to-Use, Mix-and-Read, HTS-Ready Assay

Run your enzyme reaction, add Transcreener reagents, and read your plates. The GTPase assay kit is compatible with 96, 384, and 1536-well formats.

Uncover Accurate GTPase Inhibitors

Dose-Response Assay with WT KRAS and MRTX1133. IC₅₀ = 69 nM

Tunable to Your Target

High Quality Data Under Initial Velocity Conditions

GTPase Assay Data Under Initial Velocity Conditions

Standard curves mimicking the enzymatic conversion of GTP to GDP using the Transcreener GDP FP Assay. The dynamic range of the assay can be easily tuned for different initial GTP concentrations. Excellent Z’ values are achieved even at low GDP reagent formation.

GTPase Profiling Services

Do you want to advance your program without performing an assay in-house? Our scientists can assist you!

At BellBrook, we have experts in biochemistry and enzymology that will collaborate with you to expedite your GTPase program. We can provide inhibitor potency profiling for a variety of GTPase enzymes and related proteins.

Get accurate IC50 results fast, to understand how your inhibitor interacts with other GTPases.

Lead Discovery Services Include:

Inhibitor Screening – To identify or confirm activity with the target.
Inhibitor Potency Profiling – Dose-response with target and/or related proteins. Fast IC50 results.
Mechanism of Action Studies – Kinetic analysis to define the mode of inhibition.
GTPase Profiling – Test your compounds against a variety of GTPase enzymes to eliminate off-target effects

View GTPase Profiling Services

Related Resources

Resources

Find the right resources to help you get to your solution faster.

FAQ

Protocols

Publications

Instrument Compatibility

Application Notes

Posters

Contact Us to Learn More

Please fill out the form below. We will respond quickly to get the conversation moving and learn how we can help. We keep things discrete, confidential, and professional.

“Some CROs reserve their best teams for high profile customers. If you’re not right there with them you get less experienced teams… BellBrook understands enzyme kinetics, so it made that part of the project so much easier. The larger CRO didn’t seem to have the expertise we needed in this area.”

- BioPharma Lead Discovery Program Manager

“Excellent blend of simplicity & good science. Excellent technical support”

- Director Pharma Drug Discovery Center

“The assay itself has good reproducibility and provides a clear readout on our enzyme activity. The most important piece, however, is the level of attention to our project and rapid turnaround time. The staff at BellBrook knows what they are doing.”

- Biotech Program Manager

“Through the process of developing and validating an assay for HTS applications, I generated a very nice data package of robust high quality data.”

- Biotech Research Scientist

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Frequently Asked Questions

What makes the Transcreener GDP GTPase Assay Kit different from other GTPase assays?

It directly detects GDP, the product of GTP hydrolysis, in a simple mix‑and‑read format—no coupling enzymes required. This reduces interference, speeds up workflows, and enhances sensitivity compared to traditional methods.

Can I measure GTPase, GAP, and GEF activity with this assay?

Yes. The kit measures GDP produced by GTPases and is also compatible with assays for guanine nucleotide exchange factors (GEFs) and in some cases GTPase‑activating proteins (GAPs).

Which detection modes does it support?

You have flexibility—use fluorescence polarization (FP), fluorescence intensity (FI), or TR‑FRET formats—depending on your plate reader capability. All formats use far‑red tracers to minimize compound interference.

Is the assay suitable for high-throughput screening (HTS)?

Absolutely. It’s been validated in 96-, 384-, and 1536‑well plate formats with excellent data quality (Z’ ≥ 0.7), stable reagents, and signal stability for at least 8 hours at room temperature.

How can I get started with the Transcreener GDP GTPase Assay Kit?

You can request a sample, download a detailed product manual, or contact our scientific team for assistance with assay setup, instrument compatibility, or customized experimental applications.

BellBrook Labs
1232 Fourier Drive, Suite 115
Madison, Wisconsin 53717 USA
(608) 443-2400

info@bellbrooklabs.com

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