4ATV

STRUCTURE OF A TRIPLE MUTANT OF THE NHAA DIMER, CRYSTALLISED AT LOW PH

4ATV の概要

• エントリーDOI: 10.2210/pdb4atv/pdb
• 関連するPDBエントリー: 1ZCD
• 分子名称: NA(+)/H(+) ANTIPORTER NHAA, SULFATE ION, DODECYL-ALPHA-D-MALTOSIDE (3 entities in total)
• 機能のキーワード: transporter, sodium proton antiporter, membrane protein
• 由来する生物種: ESCHERICHIA COLI
• 細胞内の位置: Cell inner membrane; Multi-pass membrane protein: P13738
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 174882.42

構造登録者

Drew, D.,Lee, C.,Iwata, S.,Cameron, A.D. (登録日: 2012-05-10, 公開日: 2013-07-10, 最終更新日: 2024-11-13)

主引用文献

Lee, C.,Yashiro, S.,Dotson, D.L.,Uzdavinys, P.,Iwata, S.,Sansom, M.S.,von Ballmoos, C.,Beckstein, O.,Drew, D.,Cameron, A.D.
Crystal structure of the sodium-proton antiporter NhaA dimer and new mechanistic insights.
J. Gen. Physiol., 144:529-544, 2014

PubMed Abstract: Sodium-proton antiporters rapidly exchange protons and sodium ions across the membrane to regulate intracellular pH, cell volume, and sodium concentration. How ion binding and release is coupled to the conformational changes associated with transport is not clear. Here, we report a crystal form of the prototypical sodium-proton antiporter NhaA from Escherichia coli in which the protein is seen as a dimer. In this new structure, we observe a salt bridge between an essential aspartic acid (Asp163) and a conserved lysine (Lys300). An equivalent salt bridge is present in the homologous transporter NapA, but not in the only other known crystal structure of NhaA, which provides the foundation of most existing structural models of electrogenic sodium-proton antiport. Molecular dynamics simulations show that the stability of the salt bridge is weakened by sodium ions binding to Asp164 and the neighboring Asp163. This suggests that the transport mechanism involves Asp163 switching between forming a salt bridge with Lys300 and interacting with the sodium ion. pKa calculations suggest that Asp163 is highly unlikely to be protonated when involved in the salt bridge. As it has been previously suggested that Asp163 is one of the two residues through which proton transport occurs, these results have clear implications to the current mechanistic models of sodium-proton antiport in NhaA.

PubMed: 25422503
DOI: 10.1085/jgp.201411219

実験手法

X-RAY DIFFRACTION (3.5 Å)