1R3J
potassium channel KcsA-Fab complex in high concentration of Tl+
Summary for 1R3J
| Entry DOI | 10.2210/pdb1r3j/pdb |
| Related | 1K4C 1K4D 1R3I 1R3K 1R3L |
| Descriptor | Antibody Fab fragment light chain, Antibody Fab fragment heavy chain, Voltage-gated potassium channel, ... (7 entities in total) |
| Functional Keywords | membrane protein, potassium channel, kcsa-fab complex, thallium |
| Biological source | Streptomyces lividans More |
| Cellular location | Cell membrane; Multi-pass membrane protein: P0A334 |
| Total number of polymer chains | 3 |
| Total formula weight | 61849.75 |
| Authors | Zhou, Y.,MacKinnon, R. (deposition date: 2003-10-02, release date: 2003-11-25, Last modification date: 2024-10-09) |
| Primary citation | Zhou, Y.,MacKinnon, R. The occupancy of ions in the K+ selectivity filter: Charge balance and coupling of ion binding to a protein conformational change underlie high conduction rates J.Mol.Biol., 333:965-975, 2003 Cited by PubMed Abstract: Potassium ions diffuse across the cell membrane in a single file through the narrow selectivity filter of potassium channels. The crystal structure of the KcsA K+ channel revealed the chemical structure of the selectivity filter, which contains four binding sites for K+. In this study, we used Tl+ in place of K+ to address the question of how many ions bind within the filter at a given time, i.e. what is the absolute ion occupancy? By refining the Tl+ structure against data to 1.9A resolution with an anomalous signal, we determined the absolute occupancy of Tl+. Then, by comparing the electron density of Tl+ with that of K+, Rb+ and Cs+, we estimated the absolute occupancy of these three ions. We further analyzed how the ion occupancy affects the conformation of the selectivity filter by analyzing the structure of KcsA at different concentrations of Tl+. Our results indicate that the average occupancy for each site in the selectivity filter is about 0.63 for Tl+ and 0.53 for K+. For K+, Rb+ and Cs+, the total number of ions contained within four sites in the selectivity filter is about two. At low concentrations of permeant ion, the number of ions drops to one in association with a conformational change in the selectivity filter. We conclude that electrostatic balance and coupling of ion binding to a protein conformational change underlie high conduction rates in the setting of high selectivity. PubMed: 14583193DOI: 10.1016/j.jmb.2003.09.022 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.9 Å) |
Structure validation
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