Sandbox WWC3: Difference between revisions
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[[Sodium channels]] <ref name ="sod">https://en.wikipedia.org/wiki/Sodium_channel</ref> are voltage gated integral membrane proteins found in muscles and neurons that selectively allow for the diffusion of sodium ions across the membrane. These proteins important for all cells but are specifically responsible initiating electrical signaling in these cells <ref name = "crystal">doi: 10.1038/nature10238</ref> and are commonly targets of drugs and mutation. Each sodium channel is composed of two subunits: the alpha subunit, which is the ion channel transmembrane domain <ref name = "sod"/>, and two beta subunits that modulate channel gating and regulate the channel expression in the membrane <ref name ="beta">PMID: 11486343</ref>. The alpha subunit is able to function independently of the beta subunit<ref name = "beta"/> . | [[Sodium channels]] <ref name ="sod">https://en.wikipedia.org/wiki/Sodium_channel</ref> are voltage gated integral membrane proteins found in muscles and neurons that selectively allow for the diffusion of sodium ions across the membrane. These proteins important for all cells but are specifically responsible initiating electrical signaling in these cells <ref name = "crystal">doi: 10.1038/nature10238</ref> and are commonly targets of drugs and mutation. Each sodium channel is composed of two subunits: the alpha subunit, which is the ion channel transmembrane domain <ref name = "sod"/>, and two beta subunits that modulate channel gating and regulate the channel expression in the membrane <ref name ="beta">PMID: 11486343</ref>. The alpha subunit is able to function independently of the beta subunit<ref name = "beta"/> . | ||
<Structure load=' | <Structure load='5EK0' size='350' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' /> | ||
==Function== | ==Function== | ||
Sodium channels initiate action potentials in nerve and muscle cells. These electrical signals initiate the contraction of muscles and the release of neurotransmitters. The electrical signal is propagated when the sodium channel allows the influx of sodium ions. These positively charged ions depolarize the resting membrane potential of -70mV to +40mV, which creates the electrical signal that is sent along the length of the cell.The initial influx of sodium ions is often activated by the binding of a neurotransmitter to receptors on the post-synaptic membrane <ref>https://en.wikipedia.org/wiki/Neurotransmission</ref>. Then, as the sodium ions depolarize the membrane potential. more sodium channels open, and the action potential moves along the length of the muscle or nerve. The channels inactivate after 1-2ms <ref name = "physio">DOI: 10.1113/jphysiol.2011.224204</ref> and the depolarization is then reversed by the efflux of potassium ions out of potassium channel<ref name ="physio"/>. This information was first discovered by Hodgkin and Huxley in 1952<ref name ="physio"/>. For more information on the role of sodium channels in electrical signaling, click [https://en.wikipedia.org/wiki/Action_potential here]. | Sodium channels initiate action potentials in nerve and muscle cells. These electrical signals initiate the contraction of muscles and the release of neurotransmitters. The electrical signal is propagated when the sodium channel allows the influx of sodium ions. These positively charged ions depolarize the resting membrane potential of -70mV to +40mV, which creates the electrical signal that is sent along the length of the cell.The initial influx of sodium ions is often activated by the binding of a neurotransmitter to receptors on the post-synaptic membrane <ref>https://en.wikipedia.org/wiki/Neurotransmission</ref>. Then, as the sodium ions depolarize the membrane potential. more sodium channels open, and the action potential moves along the length of the muscle or nerve. The channels inactivate after 1-2ms <ref name = "physio">DOI: 10.1113/jphysiol.2011.224204</ref> and the depolarization is then reversed by the efflux of potassium ions out of potassium channel<ref name ="physio"/>. This information was first discovered by Hodgkin and Huxley in 1952<ref name ="physio"/>. For more information on the role of sodium channels in electrical signaling, click [https://en.wikipedia.org/wiki/Action_potential here]. | ||
==Structure== | ==Structure== | ||
As noted above, the sodium channel consists of an alpha and two beta subunits. However, the alpha subunit is the only part necessary for the function of the channel <ref name = "sod"/>. The alpha subunit, depicted right, consists of four repeating structures, named I through IV <ref name ="struct"> DOI: 10.1111/j.1469-7793.1998.647bp.x </ref> and shown in different colors <scene name='69/696300/ | As noted above, the sodium channel consists of an alpha and two beta subunits. However, the alpha subunit is the only part necessary for the function of the channel <ref name = "sod"/>. The alpha subunit, depicted right, consists of four repeating structures, named I through IV <ref name ="struct"> DOI: 10.1111/j.1469-7793.1998.647bp.x </ref> and shown in different colors <scene name='69/696300/Right_one/1'>here</scene>. These structures consist of six transmembrane alpha helices named S1 through S6 <ref name = "struct"/>. Interestingly, each repeating subunit resembles a bacterial K+ channel <ref name = "struct"/>. These subunits fold together to form a central pore, and this complete structure resembles a bacterial Ca2+ channel <ref name = "struct"/>. | ||
=== Gating === | === Gating === | ||
The S4 segments consist of repeated motifs of a positively charged residue (usually Arg) followed by two hydrophobic residues <ref name= "crystal"/>. | The S4 segments consist of repeated motifs of a positively charged residue (usually Arg) followed by two hydrophobic residues <ref name= "crystal"/>. | ||
<scene name='69/696300/S4/1'>TextToBeDisplayed</scene> | |||
==Medical Implications== | ==Medical Implications== | ||
==References== | ==References== | ||
<references/> | <references/> | ||
