# β2E153 Residue at Loop B of GABAAR Is Involved in Agonist Stabilization and Gating Properties

## TL;DR

This study identifies a specific residue in GABAARs that plays a key role in stabilizing the receptor and influencing its function when activated by agonists.

## Contribution

The study reveals the functional role of β2E153 in the allosteric network of GABAARs, linking agonist binding to channel gating.

## Key findings

- β2E153 mutations disrupted receptor kinetics, affecting deactivation and desensitization.
- β2E153A reduced open probability and mean open times, indicating altered gating.
- β2E153 forms electrostatic interactions that stabilize the agonist-bound conformation.

## Abstract

γ-Aminobutyric acid type A receptors (GABAARs) are pentameric ligand-gated ion channels mediating fast inhibitory neurotransmission in the mammalian brain. Although recent structural and kinetic studies have advanced understandings regarding their activation mechanisms, the molecular determinants coupling agonist binding to channel gating remain unclear. We investigated the contribution of the β2E153 residue, located on loop B of the extracellular domain, to the activation of α1β2γ2 GABAARs. Macroscopic and single-channel patch clamp recordings were used to characterize two β2E153-mutants: charge reversal (β2E153K) and hydrophobic substitution (β2E153A). Both substitutions disrupted normal receptor kinetics, with β2E153K selectively accelerating deactivation and β2E153A affecting both deactivation and desensitization. Single-channel analysis showed that β2E153A reduced open probability and mean open times, consistent with altered gating transitions inferred from kinetic modeling. Structural inspection suggested that β2E153 forms electrostatic interactions with β2K196 and β2R207 to stabilize loop C and maintain the agonist-bound conformation. The disruption of this interaction likely destabilizes loop C, leading to weakened agonist binding and modified gating. Overall, our results identify β2E153 as a key element in the long-range allosteric network linking the binding site to the channel gate in GABAARs.