1.A.1.2.6
Voltage-gated K⁺ channel, Shaker. Shaker and Shab K⁺ channels are blocked by quinidine (Gomez-Lagunas, 2010). Also regulated by unsaturated fatty acids (Börjesson and Elinder, 2011).  TMSs 3 and 4 comprise the voltage sensor paddle (Xu et al. 2013).  Partially responsible for action potential repolarization during synaptic transmission (Ford and Davis 2014). Shaker K⁺ channels can be mutated in S4 to create an analogous "omega" pore (Held et al. 2018). The NMR structure of the isolated Shaker voltage-sensing domain in LPPG micelles has been reported (Chen et al. 2019). Substituting the first S4 arginine with a smaller amino acid opens a high-conductance pathway for solution cations in the Shaker K⁺ channel at rest. The cationic current does not flow through the central K⁺ pore and is influenced by mutation of a conserved residue in S2, suggesting that it flows through a protein pathway within the voltage-sensing domain (Tombola et al. 2005). The current can be carried by guanidinium ions, suggesting that this is the pathway for transmembrane arginine permeation. Tombola et al. 2005 proposed that when S4 moves, it ratchets between conformations in which one arginine after another occupies and occludes to ions in the narrowest part of this pathway. Specific resin acids activate and open voltage-gated channels  dependent on its exact binding dynamics (Silverå Ejneby et al. 2021). Charge-voltage curves of a Shaker potassium channel are not hysteretic at steady state (Cowgill and Chanda 2023). shaker is a critical sleep regulator in Drosophila (Cirelli et al. 2005).