M2 Proton Channel: Difference between revisions
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== pH Gating == | == pH Gating == | ||
The M2 channel is low-pH gated and has a 50-fold increase in proton conductance when the pH drops from 8.2 down to 4.2.<ref name="Wu" /> The His side chain, a five-membered ring, has two nitrogen atoms.<ref name="Takeuchi" /> At a pH of 7 or higher, only one nitrogen is protonated in the neutral imidazole form.<ref name="Takeuchi" /> However, at a pH of about 5.8, the second nitrogen becomes protonated and forms the cationic imidazolium form.<ref name="Takeuchi" /> This protonation causes the His residues in each monomer to move away from each other due to electrostatic repulsion.<ref name="Takeuchi" /><ref name="Lear" /><ref name="Wu" /> This allows the channel to open and allow water and protons to cross the membrane.<ref name="Lear" /><ref name="Wu" /> | The M2 channel is low-pH gated and has a 50-fold increase in proton conductance when the pH drops from 8.2 down to 4.2.<ref name="Wu" /> The His side chain, a five-membered ring, has two nitrogen atoms.<ref name="Takeuchi" /> At a pH of 7 or higher, only one nitrogen is protonated in the neutral imidazole form.<ref name="Takeuchi" /> However, at a pH of about 5.8, the second nitrogen becomes protonated and forms the cationic imidazolium form.<ref name="Takeuchi" /> This protonation causes the His residues in each monomer to move away from each other due to electrostatic repulsion.<ref name="Takeuchi" /><ref name="Lear" /><ref name="Wu" /> This allows the channel to open and allow water and protons to cross the membrane.<ref name="Lear" /><ref name="Wu" /> | ||
== Selectivity == | |||
The selectivity of this channel is based on the binding of a proton to the His37 residues in each of the α-helices in the tetramer.<ref name="Takeuchi" /><ref name="Lear" /><ref name="Wu" /> Without protons binding to the His residues, the channel would not open. Also, because there is an excess amount of protons when the pH is in acidic conditions on the extracellular side of the membrane, a proton gradient is formed. Once the channel is open, the protons move with their gradient to the cytosolic side of the membrane. These protons are then used to acidify the viron.<ref name="Wu" /> | |||
== References == | == References == | ||
<references /> | <references /> | ||
