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

@article{Zhou2001ChemistryOI,
  title={Chemistry of ion coordination and hydration revealed by a K+ channel–Fab complex at 2.0 Å resolution},
  author={Yufeng Zhou and J. H. Morais-Cabral and A. Kaufman and R. MacKinnon},
  journal={Nature},
  year={2001},
  volume={414},
  pages={43-48}
}
Ion transport proteins must remove an ion's hydration shell to coordinate the ion selectively on the basis of its size and charge. To discover how the K+ channel solves this fundamental aspect of ion conduction, we solved the structure of the KcsA K+ channel in complex with a monoclonal Fab antibody fragment at 2.0 Å resolution. Here we show 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… Expand

Paper Mentions

Control of ion selectivity in potassium channels by electrostatic and dynamic properties of carbonyl ligands
TLDR
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. Expand
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.
TLDR
Electrostatic balance and coupling of ion binding to a protein conformational change underlie high conduction rates in the setting of high selectivity. Expand
Ion binding properties and structure stability of the NaK channel.
TLDR
It is found that a Ca(2+) can bind at the extracellular site as reported in the crystal structure in a partially hydrated state, or at a higher site in a full hydration state, which may result in the loss of selectivity of NaK. Expand
Selectivity in K+ channels is due to topological control of the permeant ion's coordinated state
TLDR
A simple theoretical analysis of K+ and Na+ complexation with water in the context of simplified binding site models and bulk solution reveals that water molecules and carbonyl groups can both provide K+ selective environments if equivalent constraints are imposed on the coordination number of the complex. Expand
Structural and Thermodynamic Properties of Selective Ion Binding in a K+ Channel
TLDR
It is concluded that ion selectivity in a K+ channel is a property of size-matched ion binding sites created by the protein structure. Expand
Potassium and sodium ion complexes with a partial peptide of the selectivity filter in K+ channels studied by cold ion trap infrared spectroscopy: the effect of hydration.
TLDR
The IR photodissociation spectra of M+Ac-tyrosine-NHMe(H2O) combined with quantum chemical calculations revealed that the water molecule binding sites are ion-dependent, and the ion-peptide distances are elongated significantly for the K+ complex in comparison to the Na+ complex by the addition of a single water molecule. Expand
Tuning a potassium channel--the caress of the surroundings.
TLDR
In this issue, Varma and Rempe provide a novel explanation for K+ and Na+ binding to clusters of water and of a few other ligands, and find that preferred solvation structures are sensitive to their environment, providing new insight into factors controlling selectivity. Expand
Structural Analysis of Ion Selectivity in the NaK Channel
TLDR
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. Expand
The predominant role of coordination number in potassium channel selectivity.
TLDR
It is demonstrated that the number of carbonyl oxygen atoms that surround permeating ions is the most important factor in determining ion selectivity rather than the size of the pore or the strength of the coordinating dipoles. Expand
Structural basis for ion permeation mechanism in pentameric ligand-gated ion channels
TLDR
Simulations and electrostatics calculations complemented the description of hydration in the pore and suggest that the water pentagons observed in the crystal are important for the ion to cross hydrophobic constriction barriers. Expand
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