Ion permeation in K+ channels occurs by direct Coulomb knock-on. Kopfer, D. A., Song, C., Gruene, T., Sheldrick, G. M., Zachariae, U., & de Groot, B. L. Science, 346(6207):352–355, October, 2014. arXiv: 1011.1669v3 ISBN: 1095-9203 (Electronic)\r0036-8075 (Linking)
Ion permeation in K+ channels occurs by direct Coulomb knock-on [link]Paper  doi  abstract   bibtex   
Potassium channels selectively conduct K(+) ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K(+) concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K(+) ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K(+) conduction. Crystallographic data are consistent with directly neighboring K(+) ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K(+) channels.
@article{Kopfer2014,
	title = {Ion permeation in {K}+ channels occurs by direct {Coulomb} knock-on},
	volume = {346},
	issn = {0036-8075},
	url = {http://www.sciencemag.org/cgi/doi/10.1126/science.1254840},
	doi = {10.1126/science.1254840},
	abstract = {Potassium channels selectively conduct K(+) ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K(+) concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K(+) ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K(+) conduction. Crystallographic data are consistent with directly neighboring K(+) ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K(+) channels.},
	number = {6207},
	urldate = {2014-10-16},
	journal = {Science},
	author = {Kopfer, D. A. and Song, C. and Gruene, T. and Sheldrick, G. M. and Zachariae, U. and de Groot, B. L.},
	month = oct,
	year = {2014},
	pmid = {25324389},
	note = {arXiv: 1011.1669v3
ISBN: 1095-9203 (Electronic){\textbackslash}r0036-8075 (Linking)},
	pages = {352--355},
}

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