PDBsum entry 2ih3

Membrane protein

PDB id: 2ih3

Contents

Protein chains

219 a.a. *

212 a.a. *

98 a.a. *

Ligands

1EM

Metals

__K ×7

Waters ×266

* Residue conservation analysis

PDB id:

2ih3

Name:

Membrane protein

Title:

Ion selectivity in a semi-synthetic k+ channel locked in the conductive conformation

Structure:

Fab heavy chain. Chain: a. Fab light chain. Chain: b. Voltage-gated potassium channel. Chain: c. Engineered: yes. Mutation: yes

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Cell_line: hybridoma. Streptomyces lividans. Organism_taxid: 1916. Gene: kcsa, skc1. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Dodecamer (from PDB file)

Resolution:

1.72Å R-factor: 0.233 R-free: 0.242

Authors:

F.I.Valiyaveetil,M.Leonetti,T.W.Muir,R.Mackinnon

Key ref:

F.I.Valiyaveetil et al. (2006). Ion selectivity in a semisynthetic K+ channel locked in the conductive conformation. Science, 314, 1004-1007. PubMed id: 17095703 DOI: 10.1126/science.1133415

Date:

25-Sep-06 Release date: 21-Nov-06

Protein chain

No UniProt id for this chain

Struc: 219 a.a.

Protein chain

No UniProt id for this chain

Struc: 212 a.a.

Protein chain

P0A334  (KCSA_STRLI) -  pH-gated potassium channel KcsA from Streptomyces lividans

Seq: 160 a.a.

Struc: 98 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

DOI no: 10.1126/science.1133415

Science 314:1004-1007 (2006)

PubMed id: 17095703

Ion selectivity in a semisynthetic K+ channel locked in the conductive conformation.

F.I.Valiyaveetil, M.Leonetti, T.W.Muir, R.Mackinnon.

ABSTRACT

Potassium channels are K+-selective protein pores in cell membrane. The selectivity filter is the functional unit that allows K+ channels to distinguish potassium (K+) and sodium (Na+) ions. The filter's structure depends on whether K+ or Na+ ions are bound inside it. We synthesized a K+ channel containing the d-enantiomer of alanine in place of a conserved glycine and found by x-ray crystallography that its filter maintains the K+ (conductive) structure in the presence of Na+ and very low concentrations of K+. This channel conducts Na+ in the absence of K+ but not in the presence of K+. These findings demonstrate that the ability of the channel to adapt its structure differently to K+ and Na+ is a fundamental aspect of ion selectivity, as is the ability of multiple K+ ions to compete effectively with Na+ for the conductive filter.

Selected figure(s)

Figure 1.
Fig. 1. Dependence of the conformation of the selectivity filter of K^+ channels on K^+ concentration. (A) Close-up view of the selectivity filter of wild-type KcsA channel in the presence of high K^+ concentrations [K^+]. Two of the diagonally opposite subunits are shown in stick representation. K^+ ions are depicted as green spheres and water molecules as red spheres. The K^+ binding sites in the selectivity filter are labeled. (B) The structure of the selectivity filter in low [K^+], represented as in (A). (C and D) Superposition of the selectivity filter of wild-type KcsA in the presence of high [K^+](blue) and low[K^+] (red). (C) shows a side view; (D) depicts a top view extending 15 Å out from the center of the filter. Aromatic residues that undergo conformation changes are indicated.

Figure 2.
Fig. 2. Structure of the selectivity filter of KcsA^D-Ala77 in the presence of high [K^+]. (A) Stereo view of the electron density of the selectivity filter of KcsA^D-Ala77. The 2F[obs] – F[calc] electron density map contoured at 2.0 for the diagonally opposite subunits is shown. (B) Structure of the selectivity filter of KcsA^D-Ala77 in high [K^+] represented as in Fig. 1. (C) Superposition of the selectivity filter of KcsA^D-Ala77 (blue) and the wild-type KcsA channel (red) in the presence of high [K^+].

The above figures are reprinted by permission from the AAAs: Science (2006, 314, 1004-1007) copyright 2006.

Figures were selected by an automated process.