Predicting Binding Affinities for the Binding Domain of Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel...

Area of Science:

• Biophysics
• Molecular Biology
• Neuroscience

Background:

• Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are critical regulators of cardiac and neuronal electrical activity.
• These channels are modulated by cyclic adenosine monophosphate (cAMP), influencing their gating and function.
• Isoform-specific differences in cAMP responsiveness are not fully understood.

Purpose of the Study:

• To determine the absolute binding free energy of cAMP to the cyclic nucleotide-binding domain (CNBD) of HCN isoforms 1-4.
• To elucidate the molecular interactions governing cAMP binding and its impact on HCN channel activation.
• To explain the varying sensitivities of different HCN isoforms to cAMP modulation.

Main Methods:

• All-atom molecular dynamics (MD) simulations were employed to model HCN channel behavior.
• The free-energy perturbation (FEP) approach was utilized to calculate binding affinities.
• Computational analysis focused on the CNBD of HCN isoforms 1-4.

Main Results:

• Absolute binding free energies of cAMP to HCN isoforms 1-4 were successfully computed.
• Quantitative insights into the energetics of cAMP-CNBD interactions were obtained.
• Differences in binding free energy across HCN isoforms were identified, correlating with known functional variations.

Conclusions:

• This study provides a detailed molecular understanding of cAMP binding to HCN channels.
• The findings offer explanations for the differential cAMP sensitivity observed among HCN isoforms.
• This work advances the comprehension of HCN channel activation and modulation mechanisms, with implications for cardiac and neurological function.