2FED

Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.317 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.248 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Separate ion pathways in a Cl-/H+ exchanger

Accardi, A.Walden, M.P.Nguitragool, W.Jayaram, H.Williams, C.Miller, C.

(2005) J.Gen.Physiol. 126: 563-570

  • DOI: 10.1085/jgp.200509417
  • Primary Citation of Related Structures:  

  • 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 bet ...

    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.


    Related Citations: 
    • Gating the selectivity filter in ClC chloride channels
      Dutzler, R.,Cambell, E.B.,Mackinnon, R.
      (2003) Science 300: 108


    Organizational Affiliation

    Department of Biochemistry, Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02454, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
H(+)/Cl(-) exchange transporter clcA
A, B
465Escherichia coli (strain K12)Mutation(s): 1 
Gene Names: clcA (eriC, yadQ)
Find proteins for P37019 (Escherichia coli (strain K12))
Go to UniProtKB:  P37019
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Fab fragment, heavy chain
C, E
222N/AMutation(s): 0 
Protein Feature View is not available: No corresponding UniProt sequence found.
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
Fab fragment, light chain
D, F
211N/AMutation(s): 0 
Protein Feature View is not available: No corresponding UniProt sequence found.
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.317 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.248 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 232.274α = 90.00
b = 98.226β = 131.73
c = 170.364γ = 90.00
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling
REFMACrefinement
PHASERphasing
HKL-2000data collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-01-03
    Type: Initial release
  • Version 1.1: 2008-05-01
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance