3IGA

Potassium Channel KcsA-Fab complex in Li+ and K+

Summary for 3IGA

• Entry DOI: 10.2210/pdb3iga/pdb
• Related: 3GB7
• Descriptor: Antibody Fab Fragment heavy chain, Antibody Fab fragment light chain, Voltage-gated potassium channel, ... (6 entities in total)
• Functional Keywords: kcsa, lithium, lithium block, potassium channel, membrane protein, cell membrane, ion transport, ionic channel, membrane, transmembrane, transport, voltage-gated channel, transport protein
• Biological source: Streptomyces lividans; More
• Cellular location: Cell membrane; Multi-pass membrane protein: P0A334
• Total number of polymer chains: 3
• Total formula weight: 60742.27

Authors

Thompson, A.N.,Ilsoo, K.,Panosian, T.D.,Iverson, T.M.,Allen, T.W.,Nimigean, C.M. (deposition date: 2009-07-27, release date: 2009-11-17, Last modification date: 2024-10-09)

Primary citation

Thompson, A.N.,Kim, I.,Panosian, T.D.,Iverson, T.M.,Allen, T.W.,Nimigean, C.M.
Mechanism of potassium-channel selectivity revealed by Na(+) and Li(+) binding sites within the KcsA pore.
Nat.Struct.Mol.Biol., 16:1317-1324, 2009

PubMed Abstract: Potassium channels allow K(+) ions to diffuse through their pores while preventing smaller Na(+) ions from permeating. Discrimination between these similar, abundant ions enables these proteins to control electrical and chemical activity in all organisms. Selection occurs at the narrow selectivity filter containing structurally identified K(+) binding sites. Selectivity is thought to arise because smaller ions such as Na(+) do not bind to these K(+) sites in a thermodynamically favorable way. Using the model K(+) channel KcsA, we examined how intracellular Na(+) and Li(+) interact with the pore and the permeant ions using electrophysiology, molecular dynamics simulations and X-ray crystallography. Our results suggest that these small cations have a separate binding site within the K(+) selectivity filter. We propose that selective permeation from the intracellular side primarily results from a large energy barrier blocking filter entry for Na(+) and Li(+) in the presence of K(+), not from a difference of binding affinity between ions.

PubMed: 19946269
DOI: 10.1038/nsmb.1703

Experimental method

X-RAY DIFFRACTION (2.75 Å)