1jvm
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KCSA POTASSIUM CHANNEL WITH TBA (TETRABUTYLAMMONIUM) AND RUBIDIUM
OverviewOverview
The K+ selectivity filter catalyses the dehydration, transfer and rehydration of a K+ ion in about ten nanoseconds. This physical process is central to the production of electrical signals in biology. Here we show how nearly diffusion-limited rates are achieved, by analysing ion conduction and the corresponding crystallographic ion distribution in the selectivity filter of the KcsA K+ channel. Measurements with K+ and its slightly larger analogue, Rb+, lead us to conclude that the selectivity filter usually contains two K+ ions separated by one water molecule. The two ions move in a concerted fashion between two configurations, K+-water-K+-water (1,3 configuration) and water-K+-water-K+ (2,4 configuration), until a third ion enters, displacing the ion on the opposite side of the queue. For K+, the energy difference between the 1,3 and 2,4 configurations is close to zero, the condition of maximum conduction rate. The energetic balance between these configurations is a clear example of evolutionary optimization of protein function.
About this StructureAbout this Structure
1JVM is a Single protein structure of sequence from Streptomyces lividans with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Energetic optimization of ion conduction rate by the K+ selectivity filter., Morais-Cabral JH, Zhou Y, MacKinnon R, Nature. 2001 Nov 1;414(6859):37-42. PMID:11689935
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