Download MendeleyChemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution.
Zhou, Y., Morais-Cabral, J.H., Kaufman, A., MacKinnon, R.(2001) Nature 414: 43-48
- PubMed: 11689936
- DOI: https://doi.org/10.1038/35102009
- Primary Citation of Related Structures:
1K4C, 1K4D - PubMed Abstract:
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 A 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 molecules in a cavity near its intracellular entryway. Carbonyl oxygen atoms within the selectivity filter form a very similar square antiprism around each K+ binding site, as if to mimic the waters of hydration. The selectivity filter changes its ion coordination structure in low K+ solutions. This structural change is crucial to the operation of the selectivity filter in the cellular context, where the K+ ion concentration near the selectivity filter varies in response to channel gating.
Organizational Affiliation:
Department of Molecular Biophysics and Biochemistry, Yale University, 260 Whitney Avenue, New Haven, Connecticut 06520, USA.
