Ion Channels

  1. Channels
    • V-G
    • Ligand-g: extracellular; intracellular
    • Stretch- and Heat activated
  2. VG channels
    • highly selective
    • how K channels so selective- allow 1 Na for every Na? b/c energetically fav to K and carobnyl oxygens
    • -tetramer (K) or pseudotetramer (Na&Ca)
    • -6 transmembrane spaing segments
    • -P region- between 5 & 6, affect permeation (ion sensitivity, block by drugs/toxins)
    • -Voltage sensor: alt sew of hydrophob & basic POSITIVE aa; ever 3rd i slysine or arginine
    • -"ball and chain"
  3. Imembrane
  4. VG K
    delayed rectifier K channel
  5. VG Na
    Inactivation-> refractory period
  6. VG Cl-
    ? inhibitory effect, usually by inc "leakage" g NOT hyperpol cell
  7. VG Ca
    • conversion of elect->chem signal
    • vesicle fusion, gen xpression, kinase activation
  8. use-dependent block
    • drug more potent as AP firing is higher.
    • higher affin to depol confirmation (slowere unbinding rate)
    • binds to inactivated channel and block
    • helps with fast arrythmias, specific
  9. Facts
    • Acquired autoimmune responses against channels may accompany cancers.
    • Channelopathies affectin excitable tissue-> brain, heart, m, brain
    • pt/missense mutations
  10. 3 features of excitable tissue disorders
    • 1. autosomal dominant
    • 2. episodic attacks
    • 3. affect a SINGLE organ- many isoforms, specific for that tissue
  11. myotonia
    • goats with myotonia also
    • lower AP
    • slower subthresh response
    • increased R-> dec g of Cl-
  12. Cl- channel-based myotnia
    • Cl is passive, voltage determines what it does (instead of other way round)
    • Cl moven in/out until Nernst pot for Cl = resting pot
  13. both myotonia & PP
    excessive Na current, NOT a Cl g defect
  14. Na gain of function defect
    • persistent Na current (incomplete inact, enhanced activ)
    • DEPOLARIZATION->-> in turn inactiv wt and mutant Na channels-> refractory-> flaccid paralysis!!
Card Set
Ion Channels
Voltage gated membrane buiophy and ion channels