BLG 311 Lecture Notes - Lecture 4: Transmembrane Protein, Oligodendrocyte, Voltage-Gated Ion Channel
29 Dec 2017
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Document Summary
How does a k+ channel select k+ and excludes na+: using the bacterial k+ channel, there are 4 subunits/components to the channel. Pore is filled with oxygen that have a negative charge and therefore attract potassium. Negatively charged amino acids of cytosolic side of the pore attracts positively charged ions. The vestibule acts as a hydrating volume (contains h2o that attracts ions to them) The selectivity filter allows only k+ to pass: contains carbonyl oxygens with a partial negative change that displaces interactions. The four carbonyl groups located in the selectivity filter can interact with k+ but not with na+ (complete dehydration of k+) Protein carbonyl molecules can interact with potassium but not with sodium because sodium ions are too small. It cannot reach the 4 oxygens on the proteins at the same time because sodium is not a big enough molecule.
