Figure 2

Three-dimensional structure and ion-conduction channel of DHPR complex.

(a) Three-dimensional structure. Left, side view (“diamond”), viewed vertical to the pseudo-4-fold axis; Midle, top view, obtained by a down-wards rotation of 90° of the “diamond” view along the horizontal axis; Right, bottom view, obtained by a down-wards rotation of 180° of the top view along the horizontal axis. Structural features (main body, hook, leg, trapezoid, tetrahedroid & central depression) are indicated by arrows. The central depressions (indicated by red arrows) on both sides of the rectangular-shaped main body of DHPR suggest that these could be the openings of the ion-conduction channel. (b) Ion-conduction channel. Upper panel, a cut-through view of the channel in vertical direction. The positions of putative membrane, the ion selectivity filter and the gate are indicated. Lower panel, sections of the channel in horizontal direction. The slices, from slice 1 to slice 18, contain the putative transmembrane region of DHPR, viewed from extracellular side to the cytoplasmic side. The distance between slices is 2 pixels (1.43 Å/pixel); the thickness of each slice is 2 pixels. The putative selectivity filter and the gate are located in slice 5 and slice 18, respectively.