Ion channels Flashcards
T/F. Patch-clamp studies only involve a single form of clamp-membrane configurations
False, you can look at whole cell, inside-out, outside-in, etc
two intrinsic properties of an ion channel
selectivity and gating
T/F. Anion channels are as abundant as cation channels
False, cation channels much more prevalent`
Largest family of ion channels
ligand-gated (ligands = GABA, ACh, etc)
T/F. Ion channels typically multimers.
True, pentameric/trimeric ligand-gating common, hexameric gap junctions, etc
Potassium voltage gated channel structure (6)
- Tetrameric
- 4 subunits identical, must come together
- Homo or hetermodimeric
- Both N and C terminus inside cell
- 6 transmembrane segments for 1 subunit
- S1-S4 voltage sensing, S4 charge capacitor, S5-S6 pore forming
Sodium voltage gated channel structure (5)
- Psuedotetrameric , 4 domains with 6 transmembrane regions - not identical
- Large central cavity, activation gate
- S1-S4 voltage sensing, S5-S6 pore
- S1-S4 in domain 4 responsible for fast inactivation
- Sodium partially hydrated as it goes through
K channel selectivity due to (3)
hydration shell, size of pore, charges lining pore
Main physiological function of Na voltage gated channels
Secretion - vesicular release of hormones and neurotransmitters
How does hydration state of ions vary for K and Na ion channels?
K completely dehydrated, Na partially hydrated
Main physiological function of Ca channels?
important second messenger in vesicle release and fusion
How can you identify new ion channel molecules
Genetic mutants/disease, biochemistry, expression cloning, RNAi
Only main free anion in physiological systems
Chloride
How can you determine ion channel specificity
Clone channel, see if you have high homology to pore selectivity for certain ions
