PDBsum entry 6adc

Transport protein

PDB id: 6adc

Contents

Protein chains

442 a.a.

222 a.a.

211 a.a.

Ligands

BXA ×2

PDB id:

6adc

Name:

Transport protein

Title:

Crystal structure of the e148a mutant clc-ec1 in the presence of 50mm bromoacetate

Structure:

H(+)/cl(-) exchange transporter clca. Chain: a, b. Synonym: clc-ec1. Engineered: yes. Mutation: yes. Other_details: sf file contains friedel pairs.. Antibody fab fragment, heavy chain. Chain: c, e. Antibody fab fragment, light chain.

Source:

Escherichia coli (strain k12). Organism_taxid: 83333. Strain: k12. Gene: clca, eric, yadq, b0155, jw5012. Expressed in: escherichia coli. Expression_system_taxid: 562. Mus musculus. Organism_taxid: 10090. Cell_line: hybridoma cell line.

Resolution:

3.06Å R-factor: 0.228 R-free: 0.275

Authors:

H.-H.Lim,K.Park

Key ref:

K.Park et al. (2019). Mutation of external glutamate residue reveals a new intermediate transport state and anion binding site in a CLC Cl^-/H⁺ antiporter. Proc Natl Acad Sci U S A, 116, 17345-17354. PubMed id: 31409705 DOI: 10.1073/pnas.1901822116

Date:

31-Jul-18 Release date: 28-Aug-19

Protein chains

P37019  (CLCA_ECOLI) -  H(+)/Cl(-) exchange transporter ClcA from Escherichia coli (strain K12)

Seq: 473 a.a.

Struc: 442 a.a.*

Protein chains

No UniProt id for this chain

Struc: 222 a.a.

Protein chains

No UniProt id for this chain

Struc: 211 a.a.

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1073/pnas.1901822116

Proc Natl Acad Sci U S A 116:17345-17354 (2019)

PubMed id: 31409705

Mutation of external glutamate residue reveals a new intermediate transport state and anion binding site in a CLC Cl^-/H⁺ antiporter.

K.Park, B.C.Lee, H.H.Lim.

ABSTRACT

The CLC family of proteins are involved in a variety of physiological processes to control cellular chloride concentration. Two distinct classes of CLC proteins, Cl^- channels and Cl^-/H⁺ antiporters, have been functionally and structurally investigated over the last several decades. Previous studies have suggested that the conformational heterogeneity of the critical glutamate residue, Glu_ex, could explain the transport cycle of CLC-type Cl^-/H⁺ antiporters. However, the presence of multiple conformations (Up, Middle, and Down) of the Glu_ex has been suggested from combined structural snapshots of 2 different CLC antiporters: CLC-ec1 from Escherichia coli and cmCLC from a thermophilic red alga, Cyanidioschyzon merolae Thus, we aimed to investigate further the heterogeneity of Glu_ex-conformations in CLC-ec1, the most deeply studied CLC antiporter, at both functional and structural levels. Here, we show that the crystal structures of the Glu_ex mutant E148D and wild-type CLC-ec1 with varying anion concentrations suggest a structural intermediate, the "Midlow" conformation. We also found that an extra anion can be located above the external Cl^--binding site in the E148D mutant when the anion concentration is high. Moreover, we observed that a carboxylate in solution can occupy either the external or central Cl^--binding site in the ungated E148A mutant using an anomalously detectable short carboxylic acid, bromoacetate. These results lend credibility to the idea that the Glu_ex can take at least 3 distinct conformational states during the transport cycle of a single CLC antiporter.