Lecture0310final - Ion channels general structure This...

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Ion channels – general structure This change in conformation that  opens the channel can be driven by The binding of ligands (small  molecules or other proteins) to the  channel    -  ligand-gated channels Changes in membrane potential  - voltage-gated channels Distortion of the bilayer  -  mechanosensitive channels Temperature  – temperature - sensitive channels
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ion channels - gating So a given channel protein can be  named according to: What gates it What ions pass through it. “Voltage-gated potassium channel” “cGMP-gated potassium channel” Channels also fall into evolutionary  families or super-families. Channels with  similar gating mechanisms tend to have  similar structures and sequences E.g. “voltage-gated channel family”   “cyclic nucleotide-gated channel family”
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Ligand-gated channels Ligand gated channels – ligands  bind  reversibly to a specific binding site on the  extracellular or intracellular surface of the  channel, much like the active site of an  enzyme. Binding initiates a conformational change  that opens the channel (stabilizes the  open state and increases its probability of  occurrence) Extracellular ligands Water-soluble hormones, neurotransmitters Intracellular ligands Small intracellular messenger molecules –  cAMP, cGMP, calcium ions Also interactions with domains of other  proteins can gate channels
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The use of Ligand-gated channels Usually, animal cells and many plant  cells maintain “resting” membrane  potentials of about –70 mV.  Ligand-gated channels are channels  which open (are gated by) the arrival and 
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Lecture0310final - Ion channels general structure This...

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