9-4-09 Structure and diseases of ion channels

9-4-09 Structure and diseases of ion channels -...

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Structure and diseases of  Structure and diseases of  ion channels ion channels Dr. McKemy 9/10/08
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Topology of principal subunits of voltage-gated Na Topology of principal subunits of voltage-gated Na +     and K and K channels channels
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Topology of voltage-gated Na Topology of voltage-gated Na +  and K  and K +  channels  channels K + -channels are tetrameric proteins. 6 transmembrane (S) domains and 1 P-segment. + S4 contains many (+)-charges residues. The voltage sensor . o The N-terminal domain is the inactivating segment. Na + -channels are monomeric proteins. Contain 4-homologous domains. + Each is structurally like the K + - channel subunits. Only one inactivating domain. + Between the III & IV transmembrane domains. The analogous S4 domains are the voltage sensors.
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Positively charged amino acids in the 4 Positively charged amino acids in the 4 th th     transmembrane domain transmembrane domain
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How do these channels “sense” voltage? Voltage-gated channels. Closed at resting MP. Depolarization opens these channels. + > depolarization, the > Na + influx. Structural changes that lead to gating. At rest, the cytosolic gate is closed. Depolarization is “sensed” by (+)-charged α -helices. + Move towards the
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9-4-09 Structure and diseases of ion channels -...

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