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Published on: January 24, 2025
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An active allosteric mechanism in ASAP1-mediated Arf1 GTP hydrolysis redefines PH domain function
Olivier Soubias1,2, Samuel L Foley3, Xiaoying Jian2
1Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA.
Nature Communications
|October 1, 2025
Summary
The ASAP1 Pleckstrin Homology domain actively regulates Arf1 GTP hydrolysis, challenging passive membrane recruitment models. This allosteric mechanism directly modulates GTPase activity, impacting cancer progression and related oncoproteins.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Signaling
Background:
- GTPase-activating proteins (GAPs) regulate small GTPases.
- ASAP1, a GAP, stimulates Arf1 GTP hydrolysis and is linked to cancer.
- ASAP1's Pleckstrin Homology (PH) domain is crucial for Arf1 regulation.
Purpose of the Study:
- To investigate the role of the ASAP1 PH domain in Arf1 GTP hydrolysis.
- To determine if PH domains actively modulate GTPase activity beyond membrane recruitment.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy
- Molecular dynamics simulations
- Kinetic assays
- Mutational analysis
Main Results:
- The ASAP1 PH domain actively binds Arf·GTP at the membrane, inducing an active state for hydrolysis.
- Key residues mediating this allosteric mechanism were identified on both ASAP1 PH domain and Arf1.
- Mathematical modeling indicated this allosteric contribution is significant for GTPase activation.
Conclusions:
- PH domains can directly and actively modulate small GTPase function.
- This active allosteric mechanism has broad implications for understanding Arf1 regulation and related oncoprotein families like Ras and Rho.
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