1R3K

potassium channel KcsA-Fab complex in low concentration of Tl+

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.238 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history. 

Literature

The occupancy of ions in the K+ selectivity filter: Charge balance and coupling of ion binding to a protein conformational change underlie high conduction rates

Zhou, Y., MacKinnon, R.

(2003) J.Mol.Biol. 333: 965-975

  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    • Potassium ions diffuse across the cell membrane in a single file through the narrow selectivity filter of potassium channels. The crystal structure of the KcsA K+ channel revealed the chemical structure of the selectivity filter, which contains four ...

    Potassium ions diffuse across the cell membrane in a single file through the narrow selectivity filter of potassium channels. The crystal structure of the KcsA K+ channel revealed the chemical structure of the selectivity filter, which contains four binding sites for K+. In this study, we used Tl+ in place of K+ to address the question of how many ions bind within the filter at a given time, i.e. what is the absolute ion occupancy? By refining the Tl+ structure against data to 1.9A resolution with an anomalous signal, we determined the absolute occupancy of Tl+. Then, by comparing the electron density of Tl+ with that of K+, Rb+ and Cs+, we estimated the absolute occupancy of these three ions. We further analyzed how the ion occupancy affects the conformation of the selectivity filter by analyzing the structure of KcsA at different concentrations of Tl+. Our results indicate that the average occupancy for each site in the selectivity filter is about 0.63 for Tl+ and 0.53 for K+. For K+, Rb+ and Cs+, the total number of ions contained within four sites in the selectivity filter is about two. At low concentrations of permeant ion, the number of ions drops to one in association with a conformational change in the selectivity filter. We conclude that electrostatic balance and coupling of ion binding to a protein conformational change underlie high conduction rates in the setting of high selectivity.

    Organizational Affiliation: 

    Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute and Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Antibody Fab fragment light chain
A
212Mus musculusMutation(s): 0 
Gene Names: Igkc
Find proteins for P01837 (Mus musculus)
Go to UniProtKB:  P01837
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Antibody Fab fragment heavy chain
B
219Mus musculusMutation(s): 0 
Gene Names: Ighg1 (Igh-4)
Find proteins for P01868 (Mus musculus)
Go to UniProtKB:  P01868
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
Voltage-gated potassium channel
C
124Streptomyces lividansMutation(s): 2 
Gene Names: kcsA (skc1)
Find proteins for P0A334 (Streptomyces lividans)
Go to UniProtKB:  P0A334
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
TL
Query on TL
Download SDF File 
Download CCD File 
C
THALLIUM (I) ION
Tl
ZLUSCZLCHQSJRU-UHFFFAOYSA-N
 Ligand Interaction
DGA
Query on DGA
Download SDF File 
Download CCD File 
C
DIACYL GLYCEROL
C39 H76 O5
UHUSDOQQWJGJQS-QNGWXLTQSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.238 
  • Space Group: I 4
Unit Cell:
Length (Å)Angle (°)
a = 154.180α = 90.00
b = 154.180β = 90.00
c = 75.050γ = 90.00
Software Package:
Software NamePurpose
CNSphasing
SCALEPACKdata scaling
CNSrefinement
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots


View more in-depth experimental data

Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-11-25
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance