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Our work concerns a few particular channel types. One is a voltage-gated potassium channel, called Shaker after the name of a misbehaving fruit fly that lacks this channel's gene. Another is a member of the same voltage-gated channel family, but is also controlled by ligands, namely calcium ions. When open it allows a large current of potassium ions to flow, and so is known as the BK (big K+) channel. The third is an intracellular calcium-release channel called the IP3 receptor. It opens in response to the binding of an important intracellular messenger molecule, inositoltrisphosphate, and releases calcium ions from intracellular stores.

Mechanism of Voltage Sensing in Shaker Potassium Channels

The S4 region is the main voltage sensing region in the 6TM (six transmembrane segment) voltage-gated channel family. Baker et al. (1998) introduced a cysteine residue into the middle of S4 (F370C) of the Shaker channel. They found that modification of this residue with MTSET resulted in the loss of channel currents. Did this mean that the voltage sensor was locked in the "deactivated" position? We have examined ionic currents and gating currents in channels with cysteine mutations in positions 370 to 374 of Shaker. In none of these are gating currents entirely abolished by MTSET applied to the intracellular membrane surface, but the voltage dependence of gating charge is shifted.