Atomic structure of a Na+- and K+-conducting channel

@article{Shi2006AtomicSO,
  title={Atomic structure of a Na+- and K+-conducting channel},
  author={Ning Shi and Sheng Ye and Amer Alam and Liping Chen and Youxing Jiang},
  journal={Nature},
  year={2006},
  volume={440},
  pages={570-574}
}
Ion selectivity is one of the basic properties that define an ion channel. Most tetrameric cation channels, which include the K+, Ca2+, Na+ and cyclic nucleotide-gated channels, probably share a similar overall architecture in their ion-conduction pore, but the structural details that determine ion selection are different. Although K+ channel selectivity has been well studied from a structural perspective, little is known about the structure of other cation channels. Here we present crystal… 

Gating at the selectivity filter of ion channels that conduct Na+ and K+ ions.

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Equilibrium selectivity alone does not create K+-selective ion conduction in K+ channels.

The variants of the non-selective Bacillus cereus NaK cation channel the authors examine are all selective for K(+) over Na(+) ions at equilibrium, and the detailed architecture of the K(+ channel selectivity filter, and not only its equilibrium ion preference, is fundamental to the generation of selectivity during ion conduction.
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References

SHOWING 1-10 OF 29 REFERENCES

The structure of the potassium channel: molecular basis of K+ conduction and selectivity.

The architecture of the pore establishes the physical principles underlying selective K+ conduction, which promotes ion conduction by exploiting electrostatic repulsive forces to overcome attractive forces between K+ ions and the selectivity filter.

A functional connection between the pores of distantly related ion channels as revealed by mutant K+ channels.

It is demonstrated that very small differences in the primary structure of an ion channel can account for extreme functional diversity, and they suggest a possible connection between the pore-forming regions of K+, Ca2+, and cyclic nucleotide-gated ion channels.

Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands

Molecular dynamics simulations for the potassium channel KcsA show that the carbonyl groups coordinating the ion in the narrow pore are indeed very dynamic (‘liquid-like’) and that their intrinsic electrostatic properties control ion selectivity.

Chemistry of ion coordination and hydration revealed by a K+ channel–Fab complex at 2.0 Å resolution

Here it is shown how the K+ channel displaces water molecules around an ion at its extracellular entryway, and how it holds a K+ ion in a square antiprism of water molecules in a cavity near its intracellular entry way.

The Barium Site in a Potassium Channel by X-Ray Crystallography

Structural and functional data imply that at physiological ion concentrations a third ion may interact with two ions in the selectivity filter, perhaps by entering from one side and displacing an ion on the opposite side.

Single Streptomyces lividans K+ Channels: Functional Asymmetries and Sidedness of Proton Activation

Results demonstrate unambiguously that the protonation sites linked to gating are on the intracellular portion of the KcsA protein.

Functional Asymmetries and Sidedness of Proton Activation

These results demonstrate unambiguously that the protonation sites linked to gating are on the intracellular portion of the KcsA protein, which provides compelling explanations for ion permeation and gating phenomena observed over many years in a multitude of K 1 channels.

Cyclic nucleotide-gated ion channels.

CNG channels are nonselective cation channels that do not discriminate well between alkali ions and even pass divalent cations, in particular Ca2+.