C1-linker region of PARG1 RhoGAP promotes the catalytic recognition fold of RhoA substrate

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• PARG1 (ArhGAP29) is an F-BAR protein with a Rho GTPase-activating protein (GAP) domain.
• RhoGAP proteins regulate Rho GTPases, crucial for cellular processes.
• Understanding PARG1's substrate specificity is key to its function.

Purpose of the Study:

• To structurally model and computationally analyze the substrate-recognition mechanism of human PARG1.
• To investigate the role of specific domains and mutations in PARG1-RhoA interaction.

Main Methods:

• Computational modeling including HDOCK docking analysis.
• Molecular dynamics simulations of wild-type and mutant PARG1-RhoA complexes.
• Analysis of interface residues, structural determinants, and binding affinities.

Main Results:

• The RhoGAP domain, with the N-terminal C1 region, specifically recognizes RhoA via its catalytic loop and helices.
• Wild-type PARG1 forms a stable interaction with RhoA through unique interfaces involving the C1 domain and RhoA's α3 helix.
• Mutations (T622M, I845V) alter RhoA interaction, with I845V disorganizing interfaces and T622M reducing substrate affinity.

Conclusions:

• The C1 domain and GAP region motions are critical for wild-type PARG1's stable RhoA interaction.
• Mutant PARG1 GAP domains exhibit altered dynamics, leading to disorganized catalytic complexes.
• Structural insights into PARG1-RhoA binding provide a basis for understanding its regulatory role.