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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Bostick, David L. Brooks, Charles L. |
| Description | Author Affiliation: Bostick DL ( Department of Molecular Biology and Center for Theoretical Biological Physics, The Scripps Research Institute, 10550 North Torrey Pines Road, TPC 6, La Jolla, CA 92037, USA.); |
| Abstract | The selectivity filter of K+ channels provides specific coordinative interactions between dipolar carbonyl ligands, water, and the permeant cation, which allow for selective flow of K+ over (most importantly) Na+ across the cell membrane. Although a structural viewpoint attributes K+ selectivity to coordination geometry provided by the filter, recent molecular dynamics simulation studies attribute it to dynamic and unique chemical/electrostatic properties of the filter's carbonyl ligands. Here we provide a simple theoretical analysis of K+ and Na+ complexation with water in the context of simplified binding site models and bulk solution. Our analysis reveals that water molecules and carbonyl groups can both provide K+ selective environments if equivalent constraints are imposed on the coordination number of the complex. Absence of such constraints annihilates selectivity, demonstrating that whether a coordinating ligand is a water molecule or a carbonyl group, 'external' or 'topological' constraints/forces must be imposed on an ion-coordinated complex to elicit selective binding. These forces must inevitably originate from the channel protein, because in bulk water, which, by definition, presents a nonselective medium, the coordination number is allowed to relax to suit the ion. We show that the coordination geometry of K+ channel binding sites is replicated by 8-fold complexation of K+ in both water and simplified binding site models due to dominance of local interactions within a complex and is thus a requirement for topologically constraining the coordination number to a specific value. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 22 |
| Volume Number | 104 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2007-05-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Ions Chemistry Potassium Channels Metabolism Binding Sites Computer Simulation Models, Biological Research Support, N.I.H., Extramural Research Support, U.S. Gov't, Non-P.H.S. Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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