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

  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},
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.

Structural studies of ion permeation and Ca2+ blockage of a bacterial channel mimicking the cyclic nucleotide-gated channel pore

The structural analysis of a set of mimics of CNG channel pores reveals that the conserved acidic residue in the filter is essential for Ca2+ binding but not through direct ion chelation as in the currently accepted view.

Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites

It is suggested that the number of contiguous ion binding sites in a single file is the key determinant of the channel’s selectivity properties and the presence of four sites in K+ channels is essential for highly selective and efficient permeation of K+ ions.

Structure, function, and ion-binding properties of a K+ channel stabilized in the 2,4-ion–bound configuration

These structures validate, from a structural point of view, the notion that 2 isoenergetic ion-bound configurations coexist within a K+ channel’s selectivity filter, which fully agrees with the water–K+-ion–coupled transport detected by streaming potential measurements.

Mechanism for Variable Selectivity and Conductance in Mutated NaK Channels

This work has found that K+ and Na+ have distinct preferable binding configurations in the conductive filter of two highly K+ selective channels, which are mutated from the nonselective NaK channel and can conduct Na+ upon removal of K+.

Structural and Thermodynamic Properties of Selective Ion Binding in a K+ Channel

It is concluded that ion selectivity in a K+ channel is a property of size-matched ion binding sites created by the protein structure.

Structural insight into Ca2+ specificity in tetrameric cation channels

A detailed structural analysis of the NaK channel is presented, confirming that the Asp-66 residue, although not involved in direct chelation of Ca2+, plays an essential role in external Ca2+ binding and giving evidence for the presence of a second Ca2-binding site within theNaK selectivity filter where monovalent cations also bind.

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.



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+.