![]() Our results indicate that sodium and potassium can occupy the pore simultaneously and that multiple occupancy results in interactions between ions in the channel pore. The decrease in the apparent potassium affinity in A463C channels allows further study of possible ion interactions in the pore. ![]() The A463C mutation decreases the internal barium affinity of the channel, as expected if barium blocks current by binding to a potassium site in the pore. Independent evidence that A463C decreases the apparent affinity of a binding site in the pore comes from a study of barium block of potassium currents. We show that changing a single residue in S6, A463C, decreases the apparent internal potassium affinity of the Shaker channel pore from the micromolar to the millimolar range, as determined from the ability of potassium to block the sodium currents. The Shaker potassium channel conducts sodium poorly in the presence of very low (micromolar) potassium due to its high potassium affinity (Starkus, J.G., L. Potassium affinity, and therefore the ability to block sodium current, varies among potassium channel subtypes (Korn, S.J., and S.R. ![]() Sodium flux is blocked by the addition of low concentrations of potassium. However, in the absence of potassium, certain potassium channels can conduct sodium. ![]() Under physiological conditions, potassium channels are extraordinarily selective for potassium over other ions.
0 Comments
Leave a Reply. |