BIO254:Charge

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25 April 2024

GATING CHARGES

Voltage-gated ion channels open and close in response to changes in the electric environment of the membrane. This is achieved though a voltage sensor that detects voltage by use of key charged elements or “gating charges”. Changes in membrane potential cause motion of the gating charges thus inducing conformational changes in the whole protein and resulting in opening or closure of the channel. The opening event consists of positive charges moving outwardly while they move inwardly for closing the channels during repolarizations. The movement of these charges is detectable in voltage clamp as small current that precedes the ionic currents and is known as “gating current”. Their movement can also be detected using optical methods, where a fluorescent dye can be coupled to the outside of the channel and changes in fluorescence can be measured as the local environment changes due to charge movement. For many voltage-gated ion channels the charges are conserved positively charged amino acids and their identity has been studied extensively using mutagenesis and heterologous expression. Taken together, these studies indicate that most of the gating charges reside within the S4 segment of the channels.

For a great review see: The Voltage Sensor in Voltage-Dependent Ion Channels 'Francisco Bezanilla. Physiological Reviews, Vol. 80, No. 2, April 2000, pp. 555-592. .