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Updated: May 19, 2026
10:37
Comparing the Affinity of GTPase-binding Proteins using Competition Assays
Published on: October 8, 2015
Allosteric Biosensors Unravel GTPase-Effector Feedback
Mingyu Choi1, Roshan Ravishankar2, Lihua He1
1Department of Pharmacology, UNC Chapel Hill, Chapel Hill, NC, USA.
Biorxiv : the Preprint Server for Biology
|May 18, 2026
Summary
New biosensors for GTPases (Guanine Triphosphateases) visualize protein activity without disrupting cell function. This allows researchers to observe real-time cellular signaling, revealing previously hidden regulatory feedback loops.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Fluorescent biosensors are crucial for studying cellular signaling dynamics.
- Existing GTPase biosensors can interfere with normal cell physiology by blocking downstream protein interactions.
Purpose of the Study:
- To develop a generalizable design for GTPase biosensors that report activity without blocking effector binding.
- To investigate the spatio-temporal dynamics and regulation of GTPase activity, specifically Rac1.
Main Methods:
- Engineered GTPase biosensors (AlloRac1, AlloCdc42) by inserting circularly permuted fluorescent proteins into conserved loops.
- Utilized biosensors for quantitative imaging of GTPase activity in vivo.
- Investigated the role of effector interactions (Pak1, β-Pix) in Rac1 auto-regulation.
Main Results:
- The novel biosensors enable activity-dependent fluorescence without inhibiting ligand interactions.
- Rac1 biosensor revealed a positive auto-regulatory feedback loop involving effector interactions.
- This feedback loop modulated Rac1 activity kinetics, localization, and gradient formation, influencing cell motility.
Conclusions:
- The new biosensor design overcomes limitations of previous GTPase sensors.
- Revealed a previously unobserved auto-regulatory feedback mechanism in Rac1 signaling.
- Enables quantitative imaging of GTPase regulation, advancing understanding of cellular dynamics.
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