High-pressure studies reveal the conformational landscape of the small GTPase Arf6 and other related studies

Arf6 is a small GTPase involved in plasma membrane–endosome trafficking and displays distinct functional roles from the homologous Arf1. Given the extensive structural rearrangements during GDP/GTP switching, the study investigates whether transient, excited conformations sampled during the switch underpin binding-partner specificity. The goal is to map the conformational landscape of Arf6 to understand these excited states and their potential role in specificity.

Pressure-induced perturbation was applied to locally unfold Arf6, coupled with a two-pronged biophysical approach: high-pressure nuclear magnetic resonance (NMR) to obtain residue-specific unfolding information, and high-pressure small-angle X-ray scattering (SAXS) to derive pair-distance distribution functions and assess global shape across pressures. These datasets were integrated to map pressure-dependent conformational states.

• Developed residue-specific unfolding curves for Arf6 using high-pressure NMR.
• Generated pair-distance distribution curves from high-pressure SAXS to characterize global protein shape at various pressures.
• Initiated a structural map of the pressure-accessible conformational landscape of Arf6, providing insight into excited states that may drive binding-partner specificity.

The combined high-pressure NMR and SAXS analyses reveal pressure-accessible, excited conformations of Arf6 that likely contribute to functional specificity beyond end-state GDP/GTP structures. Mapping these intermediates provides a framework to relate dynamic conformational states during the nucleotide switch to selective interactions with non-interchangeable accessory proteins.

This study establishes a pressure-based strategy integrating residue-level (NMR) and global (SAXS) data to map the conformational landscape of Arf6. The results support a model in which excited intermediates during switching contribute to interaction specificity. Future work can extend this map, quantify populations and energetics of intermediates, and relate specific conformers to binding events with regulatory partners.