3ND0

X-ray crystal structure of a slow cyanobacterial Cl-/H+ antiporter


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.2 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.243 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Structure of a Slow CLC Cl(-)/H(+) Antiporter from a Cyanobacterium.

Jayaram, H.Robertson, J.L.Wu, F.Williams, C.Miller, C.

(2011) Biochemistry 50: 788-794

  • DOI: 10.1021/bi1019258
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • X-ray crystal structures have been previously determined for three CLC-type transporter homologues, but the absolute unitary transport rate is known for only one of these. The Escherichia coli Cl(-)/H(+) antiporter (EC) moves ∼2000 Cl(-) ions/s, an e ...

    X-ray crystal structures have been previously determined for three CLC-type transporter homologues, but the absolute unitary transport rate is known for only one of these. The Escherichia coli Cl(-)/H(+) antiporter (EC) moves ∼2000 Cl(-) ions/s, an exceptionally high rate among membrane-transport proteins. It is not known whether such rapid turnover is characteristic of ClCs in general or if the E. coli homologue represents a functional outlier. Here, we characterize a CLC Cl(-)/H(+) antiporter from the cyanobacterium Synechocystis sp. PCC6803 (SY) and determine its crystal structure at 3.2 Å resolution. The structure of SY is nearly identical to that of EC, with all residues involved in Cl(-) binding and proton coupling structurally similar to their equivalents in EC. SY actively pumps protons into liposomes against a gradient and moves Cl(-) at ∼20 s(-1), 1% of the EC rate. Electrostatic calculations, used to identify residues contributing to ion binding energetics in SY and EC, highlight two residues flanking the external binding site that are destabilizing for Cl(-) binding in SY and stabilizing in EC. Mutation of these two residues in SY to their counterparts in EC accelerates transport to ∼150 s(-1), allowing measurement of Cl(-)/H(+) stoichiometry of 2/1. SY thus shares a similar structure and a common transport mechanism to EC, but it is by comparison slow, a result that refutes the idea that the transport mechanism of CLCs leads to intrinsically high rates.


    Organizational Affiliation

    Department of Biochemistry, Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts 02454, United States.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Sll0855 protein
A, B
466Synechocystis sp. (strain PCC 6803 / Kazusa)Mutation(s): 0 
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
H+/Cl- or F- Exchange Transporters
Protein: 
H+/Cl- Eukaryotic Exchange Transporter
Find proteins for P73745 (Synechocystis sp. (strain PCC 6803 / Kazusa))
Go to UniProtKB:  P73745
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CL
Query on CL

Download SDF File 
Download CCD File 
A, B
CHLORIDE ION
Cl
VEXZGXHMUGYJMC-UHFFFAOYSA-M
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.2 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.243 
  • Space Group: P 3 2 1
Unit Cell:
Length (Å)Angle (°)
a = 203.790α = 90.00
b = 203.790β = 90.00
c = 96.820γ = 120.00
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
PHENIXrefinement
REFMACrefinement
SCALAdata scaling
PHASERphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-01-19
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance