Mechanism of potassium-channel selectivity revealed by Na+ and Li+ binding sites within the KcsA pore
| Autor: | Ilsoo Kim, Tina M. Iverson, Toby W. Allen, T.D. Panosian, Crina M. Nimigean, Ameer N. Thompson |
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| Rok vydání: | 2009 |
| Předmět: |
Potassium Channels
Sodium Potassium KcsA potassium channel chemistry.chemical_element Lithium Molecular Dynamics Simulation Protein degradation Crystallography X-Ray Article Substrate Specificity Bacterial Proteins Electricity Structural Biology Cations Binding site Molecular Biology Binding Sites Chemistry Potassium channel Protein Structure Tertiary Crystallography Biochemistry Streptomyces lividans Selectivity Intracellular |
| Zdroj: | Nature Structural & Molecular Biology. 16:1317-1324 |
| ISSN: | 1545-9985 1545-9993 |
| DOI: | 10.1038/nsmb.1703 |
| Popis: | Potassium channels allow K+ ions to easily diffuse through their pores while effectively preventing smaller Na+ ions from permeation. The ability to discriminate between these two similar and abundant ions is vital for these proteins to control electrical and chemical activity in all organisms. This selection process occurs at the narrow selectivity filter that contains structurally identified K+ binding-sites. Selectivity is thought to arise because smaller ions such as Na+ do not bind to these K+ sites in a thermodynamically favorable way. Using the model K+ channel KcsA, we examined how intracellular Na+ and Li+ interact with the pore and the permeant ions using electrophysiology, molecular dynamics simulations, and X-ray crystallography. Our results suggest that these small cations have a binding site within the K+ selectivity filter, albeit different from the K+ sites. We propose that selective permeation from the intracellular side is achieved mainly by a large energy barrier blocking filter entry for Na+ and Li+ in the presence of K+, and not by a difference of binding affinity between ions inside the selectivity filter. |
| Databáze: | OpenAIRE |
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