2FEE

Structure of the Cl-/H+ exchanger CLC-ec1 from E.Coli in NaBr

2FEE の概要

• エントリーDOI: 10.2210/pdb2fee/pdb
• 関連するPDBエントリー: 1OTS 2FEC 2FED
• 分子名称: H(+)/Cl(-) exchange transporter clcA, Fab fragment, heavy chain, Fab fragment, light chain (3 entities in total)
• 機能のキーワード: clc-ec1; clca_ecoli; chloride/proton exchange transporter, proton transport, membrane protein
• 由来する生物種: Escherichia coli; 詳細
• 細胞内の位置: Cell inner membrane; Multi-pass membrane protein (Probable): P37019
• タンパク質・核酸の鎖数: 6
• 化学式量合計: 193140.34

構造登録者

Accardi, A.,Walden, M.P.,Nguitragool, W.,Jayaram, H.,Williams, C.,Miller, C. (登録日: 2005-12-15, 公開日: 2006-01-03, 最終更新日: 2024-11-06)

主引用文献

Accardi, A.,Walden, M.P.,Nguitragool, W.,Jayaram, H.,Williams, C.,Miller, C.
Separate ion pathways in a Cl-/H+ exchanger
J.Gen.Physiol., 126:563-570, 2005

PubMed Abstract: CLC-ec1 is a prokaryotic CLC-type Cl(-)/H+ exchange transporter. Little is known about the mechanism of H+ coupling to Cl-. A critical glutamate residue, E148, was previously shown to be required for Cl(-)/H+ exchange by mediating proton transfer between the protein and the extracellular solution. To test whether an analogous H+ acceptor exists near the intracellular side of the protein, we performed a mutagenesis scan of inward-facing carboxyl-bearing residues and identified E203 as the unique residue whose neutralization abolishes H+ coupling to Cl- transport. Glutamate at this position is strictly conserved in all known CLCs of the transporter subclass, while valine is always found here in CLC channels. The x-ray crystal structure of the E203Q mutant is similar to that of the wild-type protein. Cl- transport rate in E203Q is inhibited at neutral pH, and the double mutant, E148A/E203Q, shows maximal Cl- transport, independent of pH, as does the single mutant E148A. The results argue that substrate exchange by CLC-ec1 involves two separate but partially overlapping permeation pathways, one for Cl- and one for H+. These pathways are congruent from the protein's extracellular surface to E148, and they diverge beyond this point toward the intracellular side. This picture demands a transport mechanism fundamentally different from familiar alternating-access schemes.

PubMed: 16316975

実験手法

X-RAY DIFFRACTION (3.2 Å)