1R3I

potassium channel KcsA-Fab complex in Rb+

1R3I の概要

• エントリーDOI: 10.2210/pdb1r3i/pdb
• 関連するPDBエントリー: 1K4C 1K4D 1R3J 1R3K 1R3L
• 分子名称: Antibody Fab fragment light chain, Antibody Fab fragment heavy chain, Voltage-gated potassium channel, ... (7 entities in total)
• 機能のキーワード: membrane protein, potassium channel, kcsa-fab complex, rubidium
• 由来する生物種: Streptomyces lividans; 詳細
• 細胞内の位置: Cell membrane; Multi-pass membrane protein: P0A334
• タンパク質・核酸の鎖数: 3
• 化学式量合計: 61169.71

構造登録者

Zhou, Y.,MacKinnon, R. (登録日: 2003-10-02, 公開日: 2003-11-25, 最終更新日: 2024-10-30)

主引用文献

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

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

実験手法

X-RAY DIFFRACTION (2.4 Å)