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1R3L

potassium channel KcsA-Fab complex in Cs+

Summary for 1R3L
Entry DOI10.2210/pdb1r3l/pdb
Related1K4C 1K4D 1R3I 1R3J 1R3K
DescriptorAntibody Fab fragment light chain, Antibody Fab fragment heavy chain, Voltage-gated potassium channel, ... (7 entities in total)
Functional Keywordsmembrane protein, potassium channel, kcsa-fab complex, cesium
Biological sourceStreptomyces lividans
More
Cellular locationCell membrane; Multi-pass membrane protein: P0A334
Total number of polymer chains3
Total formula weight61492.36
Authors
Zhou, Y.,MacKinnon, R. (deposition date: 2003-10-02, release date: 2003-11-25, Last modification date: 2024-10-30)
Primary citationZhou, 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: 14583193
DOI: 10.1016/j.jmb.2003.09.022
PDB entries with the same primary citation
Experimental method
X-RAY DIFFRACTION (2.41 Å)
Structure validation

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