2QTO image
Entry Detail
PDB ID:
2QTO
Title:
An anisotropic model for potassium channel KcsA
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2007-08-02
Release Date:
2007-09-25
Method Details:
Experimental Method:
Resolution:
3.20 Å
R-Value Free:
0.27
R-Value Work:
0.27
R-Value Observed:
0.27
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Voltage-gated potassium channel
Chain IDs:A, B, C, D
Chain Length:97
Number of Molecules:4
Biological Source:Streptomyces lividans
Primary Citation
Normal-mode refinement of anisotropic thermal parameters for potassium channel KcsA at 3.2 A crystallographic resolution
Structure 15 955 962 (2007)
PMID: 17698000 DOI: 10.1016/j.str.2007.06.012

Abstact

We report a normal-mode method for anisotropic refinement of membrane-protein structures, based on a hypothesis that the global near-native-state disordering of membrane proteins in crystals follows low-frequency normal modes. Thus, a small set of modes is sufficient to represent the anisotropic thermal motions in X-ray crystallographic refinement. By applying the method to potassium channel KcsA at 3.2 A, we obtained a structural model with an improved fit with the diffraction data. Moreover, the improved electron density maps allowed for large structural adjustments for 12 residues in each subunit, including the rebuilding of 3 missing side chains. Overall, the anisotropic KcsA structure at 3.2 A was systematically closer to a 2.0 A KcsA structure, especially in the selectivity filter. Furthermore, the anisotropic thermal ellipsoids from the refinement revealed functionally relevant structural flexibility. We expect this method to be a valuable tool for structural refinement of many membrane proteins with moderate-resolution diffraction data.

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