Targeting LRRK2 for Parkinson’s Disease with the Transcreener® GDP GTPase Assay

Transcreener GDP GTPase Assay Kit

The Transcreener GTPase Assay directly measures GDP produced by in vitro GTPase reactions. Use this assay for high-throughput screening of GTPase enzymes, along with GAP and GEF partners. It is compatible with virtually any enzyme that converts GTP to GDP, regardless of what other substrates are used. 

The kit comes complete with the detection reagents required to measure activity. GTPase enzyme is not included in the inhibitor screening assay kit. Please contact us for questions related to acquiring the enzyme.

Learn More About Measuring GEF and GAP Activity:

How Does The GTPase Assay Work?

The Transcreener GDP Assay determines GTPase enzyme activity by directly measuring the GDP formed by the enzyme 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 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 extremely amiable to HTS.

GTPase Enzyme Reaction Cycle

GTPase Assay On Off Schematic

GTPase Assay Applications

Below includes target applications validated using the Transcreener GTPase Assay. To learn more about an application, click on the respective target. 

GTPase FamilyEnzyme
Ras FamilyKRAS
Rho FamilyRhoA
Ran FamilyRan

Direct Detection of GDP to Measure GTPase Enzymatic Activity

Fluorescent Polarization (FP)

Transcreener GTPase Assay Schematic

The workhorse. Used in many large screens. Best deck and signal stability.

Fluorescent Intensity (FI)

Transcreener GTPase FI Readout

Positive FI signal. Compatible with simple fluorescence plate readers. Faster read time than FP or TR-FRET. 

Time-Resolved Förster Resonance Energy Transfer (TR-FRET)

Transcreener GTPase Assay TR-FRET Readout

For customers who prefer TR-FRET detection. Uses the same filter set as HTRF®


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

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

GDP GTPase Assay Schematic

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


  • 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

Assay Tunable to Your Target

GTPase Standard Curve in GTP Hydrolysis

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.

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

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.

Assay Development Services

Contact Us to Learn More

Contact us today to see if BellBrook's GTPase profiling services will advance your research. We will respond quickly to get the conversation moving and learn how we can help. We keep things discrete, confidential, and professional. 

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

SupplierInstrumentFP AssaysFI AssaysTR-FRET Assays
TriStar2S LB 942In ReviewClick Me ArrowValidatedClick Me ArrowValidated
Mithras2 LB 943In ReviewClick Me ArrowValidatedClick Me ArrowValidated
CytationTM 5ValidatedValidatedValidated
CytationTM 3ValidatedValidatedValidated
CytationTM 1ValidatedValidatedValidated
SynergyTM H1ValidatedValidatedValidated
SynergyTM 2/H4/4Click Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
SynergyTM HTXNot CapableValidatedNot Capable
SynergyTM Neo 2ValidatedValidatedValidated
POLARstar® OmegaClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
FLUOstar® OmegaNot CapableClick Me ArrowValidatedClick Me ArrowValidated
PHERAstar® FSXClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
PHERAstar® Plus/FSClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
CLARIOstar® /PlusClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
VANTAstarTMClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
SenseIn ReviewClick Me ArrowValidatedIn Review
Analyst® GT/HTClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
Gemini® XPS/EMNot CapableClick Me ArrowValidatedNot Capable
SpectraMax® M2/M2eNot CapableClick Me ArrowValidatedNot Capable
SpectraMax® M5/M5e/FlexStation® 3Not CapableClick Me ArrowValidatedClick Me ArrowValidated
SpectraMax® ParadigmClick Me ArrowValidatedClick Me ArrowContact UsClick Me ArrowContact Us
SpectraMax® iD3/iD5ValidatedClick Me ArrowValidatedClick Me ArrowValidated
EnVision®/EnVision® XciteClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
Infinite® M1000/M1000Pro/Safire2TMClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
Infinite® M200Not CapableClick Me ArrowValidatedNot Capable
Infinite® F500Click Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated
Infinite® F200/UltraevolutionClick Me ArrowContact UsClick Me ArrowValidatedClick Me ArrowContact Us
SparkTM 10MClick Me ArrowValidatedClick Me ArrowValidatedClick Me ArrowValidated

What's Included

What You Will Need

The Role of GTPases As Therapeutic Targets

GTPases are important proteins that regulate various cell functions like signal transduction, protein biosynthesis, cell adhesion, membrane remodeling and trafficking, cytoskeletal reorganization, apoptosis, autophagy, and cell motility. They are called "master regulators" of intracellular membrane traffic because they have such extensive function in cellular operation. (Stenmark 2009)

GTPase inhibitors are attractive drug discovery targets. GTPase inhibitors are explored to treat many diseases, such as cancer and neurodegenerative diseases. To better control overactivity, we need selective technologies that assess the ability to interact with the target.

Researchers can use the Transcreener GDP GTPase Assay to study GTPases for therapeutic treatments.