Figure 1
From: Allosteric coupling of the inner activation gate to the outer pore of a potassium channel
A set of conserved residues identifies a putative mechanism that is common among Shaker-related potassium channels.
(A). The interface between the inner gate and pore helix of Kv1.2 (PDB #2R9R). Residues in Kv1.2 that are important for coupling of opening to rearrangement of the outer pore come from their equivalent positions in KcsA and are shown as Van der Waals spheres (equivalent KcsA/Kv1.2 positions); Met 96/Ala 396, red; Ile 100/Val 399, blue; Phe 103/Ile 402, orange; Thr 74/Thr 373, cyan; Thr 75/Thr 374, yellow. Also shown in color only, are four of the residues that form the selectivity filter; glycine (G, blue), tyrosine (Y,yellow), glycine (G,blue) and aspartate (D, yellow). (B). An alignment between Shaker, five human Kv1 isoforms and KcsA. Identical (black) and conserved (gray) residues among all of the isoforms are shaded. Stars beneath the alignment identify the residues in Kv1.2, Shaker and KcsA that correspond to the coupling pathway proposed by Cuello et al and include: Kv1.2 I402/Shaker I470, corresponding to phenyalanine 103 in KcsA, Kv1.2 V399/Shaker V467, corresponding to isoleucine 100 in KcsA and Kv1.2 T373, T374/Shaker T441, T442, corresponding to threonine 74 and threonine 75 in KcsA. Also shown is an alanine, which corresponds to methionine 96 in KcsA; when mutated to cysteine in Shaker, the inactivation rate is modified and the affinity of the selectivity filter for potassium is reduced. The location of threonine 449 in Shaker is separately identified by an arrow in the alignment. The sequences shown are: human Kv1.1 (gi:119395748), human Kv1.2 (gi:4826782), human Kv1.3 (gi:88758565), human Kv1.4 (gi:4504817), human Kv1.5 (gi:25952087), Shaker (gi:288442), KcsA (gi:61226909). The alignment was carried out using Clustalw (http://bio.lundberg.gu.se/edu/msf2.html) and arranged into the figure by Boxshade 3.21 (http://www.ch.embnet.org/software/BOX_form.html).
