CHEM 3050 Lecture Notes - Lecture 48: Potassium Channel, Ion, Asparagine
3 May 2018
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CHEM 3050
Lecture 48
Ion Channel Selectivity
- Ion channels are more complex in structure than
porins
- Ion channels allow them (porins) to be more selective
about transport
- Multimers of alpha-helical segments
- Ion passageway in central axis is where the helices
meet
- K hannel from S.lividans
o Has 4 subunits
o Each monomer has 3 helices: 2 large and 1 small
o One helix from each subunit forms pore
o One helix from each subunit faces hydrophobic
membrane interior
- K channels are 10,000X more likely to transport
K than Na
o This is because Na is smaller
o It is also due to geometry of “selectivity filter”
o Pore narrows to ~3 Å
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