The influenza A virus M2 channel: a molecular modeling and simulation study

Area of Science:

• Structural biology
• Virology
• Membrane biophysics

Background:

• Influenza virus M2 protein forms proton-selective ion channels essential for viral replication.
• The M2 channel's low-pH activation mechanism is critical for understanding viral entry and uncoating.
• M2 protein is an integral membrane protein forming a tetrameric bundle of transmembrane helices.

Purpose of the Study:

• To elucidate the structural basis of M2 channel gating at low pH.
• To investigate the role of Histidine 37 (H37) in M2 channel activation.
• To model the proton conduction pathway in the M2 channel.

Main Methods:

• Computational modeling of the M2 transmembrane domain.
• Molecular dynamics simulations of the M2 channel with explicit water molecules.
• Analysis of protonation states of key residues (H37) and their impact on channel structure.

Main Results:

• The M2 channel exists in closed (deprotonated H37) and open (protonated H37) states.
• H37 side chains occlude the pore in the deprotonated state, blocking ion flow.
• Protonation of H37 reorients side chains, allowing a continuous water column and proton conduction.
• Simulations revealed a water wire facilitating proton permeability in the open channel state.

Conclusions:

• Low-pH activation of the M2 channel involves protonation of H37, transitioning the channel from a closed to an open state.
• The open M2 channel facilitates proton influx via a water wire, crucial for influenza virus replication.
• Structural insights into M2 gating provide potential targets for antiviral therapies.