Heavy Metal Directly Blocks Potassium Channels: An Experimental and Theoretical Approach

Area of Science:

• Biophysics
• Computational Biology
• Toxicology

Background:

• Heavy-metal cations (Pb²⁺, Hg²⁺) are environmental toxicants.
• Their direct interaction mechanisms with potassium (K⁺) channels are not fully understood.
• Modeling these interactions is challenging due to electrostatics and coordination chemistry.

Purpose of the Study:

• To investigate the molecular basis of Pb²⁺ and Hg²⁺ inhibition of K⁺ channels.
• To combine experimental electrophysiology with molecular dynamics simulations.
• To elucidate the binding sites and blocking mechanisms of these heavy metals.

Main Methods:

• Patch-clamp electrophysiology on diverse K⁺ channel families.
• Molecular dynamics (MD) simulations of the KcsA channel.
• Calculation of effective free-energy landscapes for ion binding.

Main Results:

• Pb²⁺ and Hg²⁺ suppress K⁺ currents, with Hg²⁺ being a more potent blocker.
• Simulations show preferential binding of both ions to conserved acidic residues in the extracellular vestibule.
• Binding disrupts K⁺ occupancy in the selectivity filter, impairing conduction.
• Identified metal-specific binding basins correlating with blocking behavior.

Conclusions:

• Pb²⁺ and Hg²⁺ act as outer-pore blockers via electrostatic and geometric interactions.
• This study provides a computational framework for studying multivalent ion blockers in K⁺ channels.
• Clarifies mechanistic observables in simulations of ion channel block.