PDBsum entry: 1jq1

Membrane protein

PDB id: 1jq1

Contents

Protein chains

34 a.a.*

* C-alpha coords only

PDB id:

1jq1

Name:

Membrane protein

Title:

Potassium channel (kcsa) open gate model

Structure:

Voltage-gated potassium channel. Chain: a, b, c, d. Fragment: inner transmembrane segment (residues 86-119). Engineered: yes

Source:

Streptomyces lividans. Organism_taxid: 1916. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

1 models

Authors:

Y.-S.Liu,P.Sompornpisut,E.Perozo

Key ref:

Y.S.Liu et al. (2001). Structure of the KcsA channel intracellular gate in the open state. Nat Struct Biol, 8, 883-887. PubMed id: 11573095 DOI: 10.1038/nsb1001-883

Date:

03-Aug-01 Release date: 03-Oct-01

Protein chains

P0A334  (KCSA_STRLI) -  Voltage-gated potassium channel

Seq: 160 a.a.

Struc: 34 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Key reference

DOI no: 10.1038/nsb1001-883

Nat Struct Biol 8:883-887 (2001)

PubMed id: 11573095

Structure of the KcsA channel intracellular gate in the open state.

Y.S.Liu, P.Sompornpisut, E.Perozo.

ABSTRACT

Ion channels catalyze the selective transfer of ions across the membrane in response to a variety of stimuli. These channels gate by controlling the access of ions to a centrally located water-filled pore. The crystal structure of the Streptomyces lividans potassium channel (KcsA) has allowed a molecular exploration of this mechanism. Electron paramagnetic resonance (EPR) studies have uncovered significant conformational changes at the intracellular end of the second transmembrane helix (TM2) upon gating. We have used site-directed spin labeling (SDSL) and EPR spectroscopy in an attempt to quantify the structural rearrangements of the KcsA TM2 bundle underlying the transition from the closed to the open state. Under conditions favoring the closed and open conformations, 10 intersubunit distances were obtained across TM2 segments from tandem dimer constructs. Analysis of these data points to a mechanism in which each TM2 helix tilts away from the permeation pathway, towards the membrane plane, and rotates about its helical axis, supporting a scissoring-type motion with a pivot point near residues 107-108. These movements are accompanied by a large increase in the diameter of the vestibule below the central water-filled cavity.

Selected figure(s)

Figure 3.
Figure 3. Calculated distances from 10 spin-labeled mutants in the closed and open states. a, Estimated EPR distances at pH 7 (black filled dots) and at pH 4 (open circles). Bars represent the standard deviation from three independent distance computations. Arrows indicate the direction of the distance changes from closed to open states (up is increase and down, decrease). C -C distances of diagonally related subunits from the crystal structure are shown for comparison (solid line). Dotted lines indicate the practical limits of distance determinations by electron -electron dipolar interactions ( 8 -25 Å) (ref. 12). b, Helical wheel representation from residues 100 -119. Both closed (top) and open (bottom) states are represented as pairs of helical wheel diagrams. The arrows inside the wheels in the open state represent distance changes from close to open (outward is increase and inward, decrease). The alignment of residues on the wheel relative to the permeation pathway was performed allowing for the pattern of spin -spin interaction observed in KcsA. In each case, a ribbon representation of the type of helix rearrangement is shown based on the position of residues according to the crystal structure.

Figure 4.
Figure 4. Modeling the conformational rearrangements in TM2. a, Graphical representation showing the type and extent of individual helical movements (red = closed and blue = open). Changes relative to the x-y plane ( [1], 8°), the z-axis ( [2], 8°) and the helical axis ( [3], 30°) are indicated by arrows. The backbone r.m.s. deviation between the two structures is 3.4 Å. b, Calibrated cross-sectional representation of the conformational changes (calculated using the program HOLE^26), highlighting the opening of a wide vestibule at the cytoplasmic end of the channel. The dotted line above residue 100 indicates the position of the selectivity filter. c, Mapping of blocker protection data^24 for tetraethylammonium (TEA), tetrabutylammonium (TBA) and the Raw3 ball peptide on the open structure of the KcsA inner helical bundle. Structural alignment was performed allowing for the pattern of spin -spin interaction observed in KcsA (shifted one residue downstream).

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Biol (2001, 8, 883-887) copyright 2001.

Figures were selected by an automated process.