Mapping Bidirectional Allosteric Communication in Arf GTPases | JoVE Visualize

Area of Science:

Molecular and Cellular Biology
Biochemistry
Biophysics

Background:

Arf GTPases are crucial eukaryotic signaling proteins involved in membrane trafficking, motility, and remodeling.
These proteins undergo significant conformational changes during their GDP-to-GTP nucleotide switch, which is essential for downstream signaling.
The GDP-to-GTP switch mechanism involves a functional molten globule (MG) ensemble.

Purpose of the Study:

To investigate the allosteric pathway governing the Arf GTPase nucleotide switch.
To determine how mutations in the N-terminal switch region affect the conformational stability and allosteric communication within Arf1.
To elucidate the role of the allosteric mechanism in controlling access to the functional molten globule state.

Main Methods:

High-pressure (HP) Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study Arf1.
The study utilized a specific mutation in the N-terminal switch region of Arf1 known to influence spontaneous switching.
HP switching studies were conducted to analyze the effects of the mutation on protein dynamics and stability.

Main Results:

A mutation in the N-terminal switch region of Arf1 was shown to perturb the stability of residues along an allosteric pathway extending from the N-terminus ('front') to the C-terminus ('back').
This perturbation confirms a continuous allosteric pathway facilitating communication between the 'front' and 'back' regions, modulated by the GDP ligand.
High-pressure studies revealed that the allosteric mechanism regulates access to the functional molten globule state, rather than directly altering switching rates.

Conclusions:

A continuous, bidirectional allosteric pathway exists in Arf GTPases, connecting the N-terminal and C-terminal regions.
This pathway, influenced by the GDP ligand, is critical for modulating the conformational switch mechanism.
The allosteric mechanism primarily controls entry into the functional molten globule state, underscoring its role in regulating Arf GTPase activity.