ION CHANNELS: Diagrams

Calcium Channels Potassium Channels Sodium Channels

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SODIUM CHANNELS

Voltage gated Na+ channel: α-subunit 4 repeated domains. Each domain has 6 membrane spanning subunits. Subunit 4 acts as a voltage sensor.

From University of Toronto

Non-Voltage gated Na+ channel Each subunit has 2 membrane spanning subunits. The channel is a heterotrimer.

From Lake Forest College

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POTASSIUM CHANNELS

CTX: Charybdotoxin Ball & chain: Inactivation domain From: Goldstein
Voltage-gated Shaker K+ channel	Inwardly rectifying K+ channel

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CALCIUM CHANNELS

Voltage gated Ca++ channel
From Queens University
Contains voltage sensor & Ca++ selective pore Consists of 4 internal repeated domains (I-IV) Each domain contains 6 α-helical transmembrane regions (S1-S6) Domain I: responsible for channel activation kinetics S4: Positively charged; Forms part of the voltage sensor 2 additional domains between S5 & S6: Form pore region of channel Verapamil & nifedipine bind Helix 5 & 6 regions of domain III Sequence after helix 6 of domain 4

Excitation-Contraction Coupling: Muscle

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4/14/2021