Gating by pH and Membrane Tension

Channels internal walls and external mouths contain groups that are easily ionized, such as tyrosine, or protonated, such as tryptophan, and are likely to be affected by changes in pH. The M2 transmembrane protein, encoded by influenza viruses, forms a tetrameric transmembrane channel for protons when it infects cells [15]. 

Tryptophan residues near the entrance to the channel block the central pore. The residues are mechanically responsive to changing concentrations of H+ at about pH 

Mechanosensitive channels respond to changes in membrane tension. A prokaryotic large-conductance mechanosensitive channel, MscL, opens in response to osmotic stress to form a water filled channel between 3 and 4 nm across [18]. The change in pressure on the bilayer imparts a small movement in a transmembrane helix that is then followed by a dramatic rearrangement of the transmembrane domain to a fully open state. 

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