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Updated: Nov 6, 2025
Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay
Published on: November 11, 2018
Active GTPase Pulldown Protocol
Martin J Baker1, Ignacio Rubio2,3
1Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Abstract:
Ras and its related small GTPases are important signalling nodes that regulate a wide variety of cellular functions. The active form of these proteins exists in a transient GTP bound state that mediates downstream signalling events. The dysregulation of these GTPases has been associated with the progression of multiple diseases, most prominently cancer and developmental syndromes known as Rasopathies. Determining the activation state of Ras and its relatives has hence been of paramount importance for the investigation of the biochemical functions of small GTPases in the cellular signal transduction network. This chapter describes the most broadly employed approach for the rapid, label-free qualitative and semi-quantitative determination of the Ras GTPase activation state, which can readily be adapted to the analysis of other related GTPases. The method relies on the affinity-based isolation of the active GTP-bound fraction of Ras in cellular extracts, followed by its visualization via western blotting. Specifically, we describe the production of the recombinant affinity probes or baits that bind to the respective active GTPases and the pulldown method for isolating the active GTPase fraction from adherent or non-adherent cells. This method allows for the reproducible measurement of active Ras or Ras family GTPases in a wide variety of cellular contexts.
Insights
This study presents a label-free method to measure the activation state of Ras GTPases, crucial proteins involved in cell signaling and diseases like cancer. The technique isolates active, GTP-bound Ras for analysis, aiding research into cellular functions and disease mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Signaling
Background:
- Ras and related small GTPases are key regulators of cellular functions.
- Dysregulation of these GTPases is linked to diseases, including cancer and Rasopathies.
- Understanding GTPase activation is vital for studying signal transduction.
Purpose of the Study:
- To describe a broadly employed, label-free method for determining Ras GTPase activation state.
- To enable qualitative and semi-quantitative analysis of active Ras and related GTPases.
- To facilitate the investigation of small GTPase biochemical functions.
Main Methods:
- Affinity-based isolation of the active, GTP-bound fraction of Ras from cellular extracts.
- Production of recombinant affinity probes (baits) that bind active GTPases.
- Pulldown assay for isolating active GTPase fractions from various cell types, followed by western blotting.
Main Results:
- The described method allows for rapid, label-free determination of Ras GTPase activation.
- The protocol is adaptable for analyzing other related GTPases.
- Reproducible measurement of active Ras or Ras family GTPases is achievable in diverse cellular contexts.
Conclusions:
- This method provides a robust approach for assessing Ras GTPase activation.
- It is valuable for research into the roles of small GTPases in normal physiology and disease.
- The technique supports the investigation of cellular signaling pathways involving Ras family proteins.
