Potassium Channel

2022-03-29: Ion Channel reference:

Potassium Channel #

• (Permeable to Na+ & K+)
• They repolarize following an Action Potential.
• Types:
  • Calcium activated ($K_{Ca}$) (BK, SK, IK)
  • Inwardly-rectifying ($K_{ir}$) Allows K+ inward flux moreso than outward. Closed by default. All require PIP2 for some reason.
    • ROMK ($K_{ir}1.x$)
    • Voltage-gated ($K_{ir}2.x$)
    • GIRKs (G protein-coupled inwardly-rectifying potassium channel) ($K_{ir}3.x$) - activated by PIP2?
    • KCNK3/K2P3.1,outwardly-rectifying potassium channel - phosphorylated by Protein Kinase Aα
    • ATP-sensitive ($K_{ir}6.x$)
      • Kir6.2
    • KCNQ ($K_{ir}7.x$)
      • Kir7.1 (KvLQT1) - mediates cardiac cell repolarization by terminating heart contraction.
  • Tandem pore domain (4T & 2P) (TWIK; TREK; TASK; TALK; THIK; TRESK)
    • K2P2.1 (KCNK2) (aka TREK-1).
    • K2P3.1 (KCNK3) - outwardly rectifying
  • Voltage-gated ($K_v$)
    • There are some motifs characteristic of their ion selectivity, such as TVGYG or TVGFG. They serve to prevent interactions between K+ and water molecules. Notice Y/F being cyclic; I think this is important.
    • Kv1.3 (KCNA3)
    • KCNH3
    • HCN