2FED

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


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.32 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.250 

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:  
    2FEE, 2FED, 2FEC

  • 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
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
H(+)/Cl(-) exchange transporter clcAAB465Escherichia coliMutation(s): 1 
Gene Names: clcAeriC
Find proteins for P37019 (Escherichia coli (strain K12))
Explore P37019 
Go to UniProtKB:  P37019
Protein Feature View
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Fab fragment, heavy chainCE222Homo sapiensMutation(s): 0 
Protein Feature View
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  • Reference Sequence
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
Fab fragment, light chainDF211Homo sapiensMutation(s): 0 
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.32 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.248 
  • R-Value Observed: 0.250 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 232.274α = 90
b = 98.226β = 131.73
c = 170.364γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
SCALEPACKdata scaling
PHASERphasing
REFMACrefinement
HKL-2000data reduction

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

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