Highlighting FeaturesShow central K and its nearest neighbors Show all as strands Show as strands w/K
Shown here is the crystal structure of the KcsA potassium channel of the bacterium, Streptomyces lividans. These results were obtained by cloning the channel, synthesizing large quantities, crystallizing the protein, x-diffraction, and mathematical refinement to produce a crystal structure with a resolution of 3.4 Å.
The threonine-valine-glycine-tyrosine-glycine amino acid sequence is preserved in all potassium channels discovered to date.
The K+ channel is a transmembrane protein that permits the movement of K+ according to its electrochemical gradient from the outside of the cell to the cytoplasm. Throughput rates are up to 108 ions per second, with a 10 4:1 preference for K+ over Na+. The high selectivity for K + is dependent upon the exact diameter of the the selectivity filter, which exploits the difference between K+ and Na+ in the energy required to dehydrate the ion (which is inversely dependent upon the radius of the dehydrated ion) as it passes from the aqueous external solution to the hydrophilic pore of the selectivity filter. The high throughput is favored by a very short selectivity filter, only a four amino acid sequence lining the pore of the selectivity filter (repeated in each of the four tetramers), a length of 12 Å.
The role of the AKT1 potassium channel in plant nutrition was confirmed by identifying a Arabidopsis thaliana mutant in which the AKT1 channel gene was disrupted. The mutant had a markedly lower potassium uptake and grew poorly when potassium concentrations were 100 µM or less, thereby establishing the role of this gene and this channel.
We, the curators, note with pleasure that on 8 October 2003, The Royal Swedish Academy of Sciences announced award of the 2003 Nobel Prize in Chemistry to Roderick MacKinnon, author of the paper below describing the first 3D structure of the K-channel and represented here in the Virtual Museum of Minerals and Molecules since 1998, “for discoveries concerning channels in cell membranes”, particularly “for structural and mechanistic studies of ion channels.” Sharing this prize is Peter Agre “for the discovery of water channels”, specifically, aquaporin.
Armstrong, C. 1998. “The vision of the pore” Science 280:56-57.
Doyle, D.A., J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Bulbis, S.L. Cohen, B.T. Chait, R. MacKinnon. 1998. “The structure of the potassium channel: Molecular basis of K+ conduction and selectivity.” Science 280:69-77.
Hirsch, R.E., B.D. Lewis, E.P. Spalding, and M.R. Sussman. 1998. “A role for the AKT1 potassium channel in plant nutrition.” Science 280:918-921.