Agonist Binding and G Protein Coupling in Histamine H₂ Receptor: A Molecular Dynamics Study

Area of Science:

• Structural biology
• Computational chemistry
• Pharmacology

Background:

• The histamine H2 receptor (H2R) is a key drug target for gastric acid-related disorders.
• Lack of 3D structural data hinders mechanistic understanding of H2R function.
• GPCR conformational dynamics are crucial for ligand binding and signaling.

Purpose of the Study:

• To create a 3D model of the active histamine-H2R-Gs complex.
• To investigate the conformational stability of the active H2R-Gs complex using advanced simulations.
• To determine the histamine binding mode and identify key interactions for drug design.

Main Methods:

• Homology modeling based on the β2-adrenoceptor structure.
• Conventional molecular dynamics (cMD) simulations.
• Metadynamics and Gaussian accelerated molecular dynamics (GaMD) simulations.
• Multiple walker metadynamics for binding pose determination.

Main Results:

• A preferential histamine binding pose was identified, consistent with experimental data.
• Key polar interactions at the H2R-Gs interface suggest a role in coupling selectivity.
• The active H2R-Gs complex conformation is stable on the microsecond timescale.
• Histamine alone does not stabilize the active H2R conformation.

Conclusions:

• The study provides a structural basis for understanding H2R activation and histamine binding.
• Molecular dynamics simulations are valuable tools for studying GPCR dynamics and drug design.
• The findings offer insights into H2R-Gs coupling selectivity and potential therapeutic strategies.