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Molecular Properties of Voltage Gated Channels

The Sodium Channel. Molecular Properties of Voltage Gated Channels. Ion Selectivity Charge on Mouth Size and charge near center, energy of hydration. Kandel 7-3.

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Molecular Properties of Voltage Gated Channels

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  1. The Sodium Channel Molecular Properties of Voltage Gated Channels Ion Selectivity Charge on Mouth Size and charge near center, energy of hydration Kandel 7-3

  2. Na channels belong to a family of channels (ionophores) that areallosteric (shape changing)Shape changes are modifiedby changes in membranepotential (voltage gated)Or chemicallyChemical modificationsare involved in shortterm memories (morelater). Kandel 7-11

  3. Molecular Structure of the Sodium Channel the a Subunit Stretched Out Voltage sensing by Nachannelsis achieved bythe a subunit depicted here. There are foursubunit domains (MI – IV)of six a helices each.Together these formthe pore. P portions ofthese domains providea charged lining. S4 helices are believed to provide the voltage sensing. The entire channel is a heterotetramer, made of the large glycoprotein a subunitforming the aqueous pore and voltage sensor, and three smaller polypeptide units b1 , b2. and (?), The inactivation gate is located onthe cytoplasmic side of the a subunit (recall pronase experiments). Kandel 10-9 modified

  4. Molecular Structure of the Sodium Channel The a Subunit – A View from the Top Kandel 10-10 Kandel 10-9 modified

  5. Molecular Structure of the Sodium Channel A Model of Voltage Driven S4 a Helical Rotation Kandel 10-10 Arginine residues pushed up and out convey the appearance of movement of 1 unit positive charge out of the membrane or 1 unit negative charge into the membrane Kandel 10-11

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