Structural Determinants Mediating Tertiapin Block of Neuronal Kir3.2 Channels

Area of Science:

• Molecular pharmacology
• Neuroscience
• Biophysics

Background:

• Tertiapin (TPN) is a peptide from bee venom that inhibits potassium channels.
• Previous studies suggested TPN acts as a pore blocker, but its specific interactions with neuronal Kir3 channels were unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms and structural determinants of Tertiapin's block on Kir3.2 channels.
• To validate computational predictions through experimental electrophysiology.

Main Methods:

• Molecular docking and molecular dynamics (MD) simulations with potential of mean force (PMF) calculations.
• Targeted mutagenesis of predicted TPN interaction sites in Kir3.2 channels.
• Electrophysiological measurements to assess functional channel block.

Main Results:

• A high-affinity TPN block of Kir3.2 channels involves a pore-inserting lysine side chain.
• Key interactions include hydrophobic contacts with a phenylalanine ring and electrostatic interactions with Kir3.2 turret regions.
• These interactions stabilize TPN binding, positioning it within the channel's outer vestibule and selectivity filter.

Conclusions:

• The study defines the structural basis for Tertiapin's high-affinity block of Kir3.2 channels.
• Findings reveal preferred subunit arrangements in Kir3.x heteromeric channels and TPN's binding capacity.
• This knowledge can guide the development of novel TPN variants with tailored Kir channel blocking properties.