3E8H: Crystal Structure Of The The Open Nak Channel-k+ Complex

Here we present a detailed characterization of ion binding in the NaK pore using the high-resolution structures of NaK in complex with various cations. These structures reveal four ion binding sites with similar chemical environments but vastly different ion preference. The most nonselective of all is site 3, which is formed exclusively by backbone carbonyl oxygen atoms and resides deep within the selectivity filter. Additionally, four water molecules in combination with four backbone carbonyl oxygen atoms are seen to participate in K(+) and Rb(+) ion chelation, at both the external entrance and the vestibule of the NaK filter, confirming the channel's preference for an octahedral ligand configuration for K(+) and Rb(+) binding. In contrast, Na(+) binding in the NaK filter, particularly at site 4, utilizes a pyramidal ligand configuration that requires the participation of a water molecule in the cavity. Therefore, the ability of the NaK filter to bind both Na(+) and K(+) ions seemingly arises from the ions' ability to use the existing environment in unique ways, rather than from any structural rearrangements of the filter itself.
PDB ID: 3E8HDownload
MMDB ID: 68651
PDB Deposition Date: 2008/8/19
Updated in MMDB: 2008/12
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 3E8H: tetrameric; determined by author and by software (PISA)
Molecular Components in 3E8H
Label Count Molecule
Proteins (4 molecules)
Potassium Channel Protein
Molecule annotation
Chemicals (13 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB