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|1k4c, resolution 2.00Å ()|
Potassium Channel KcsA-Fab complex in high concentration of K+
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.
Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution., Zhou Y, Morais-Cabral JH, Kaufman A, MacKinnon R, Nature. 2001 Nov 1;414(6859):43-8. PMID:11689936
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
1k4c is a 3 chain structure with sequence from Mus musculus and Streptomyces lividans. The February 2003 RCSB PDB Molecule of the Month feature on Potassium Channels by Shuchismita Dutta and David S. Goodsell is 10.2210/rcsb_pdb/mom_2003_2. Full crystallographic information is available from OCA.
- Zhou Y, Morais-Cabral JH, Kaufman A, MacKinnon R. Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution. Nature. 2001 Nov 1;414(6859):43-8. PMID:11689936 doi:http://dx.doi.org/10.1038/35102009
- Morais-Cabral JH, Zhou Y, MacKinnon R. Energetic optimization of ion conduction rate by the K+ selectivity filter. Nature. 2001 Nov 1;414(6859):37-42. PMID:11689935 doi:http://dx.doi.org/10.1038/35102000
- Valiyaveetil FI, Zhou Y, MacKinnon R. Lipids in the structure, folding, and function of the KcsA K+ channel. Biochemistry. 2002 Sep 3;41(35):10771-7. PMID:12196015
- Flavell RR, Muir TW. Expressed protein ligation (EPL) in the study of signal transduction, ion conduction, and chromatin biology. Acc Chem Res. 2009 Jan 20;42(1):107-16. PMID:18939858 doi:10.1021/ar800129c