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Figure 2.
Figure 2. (a) Electron density around the distal and proximal QB
positions in the structure of this work (pH 8, dark-adapted state; PDB
entry 2j8c). The 0.2 and the 1σ levels of the
density are depicted in blue and magenta wireframes, respectively. The
models for the distal (orange) and the proximal (yellow) positions are
shown as stick model. The two head-groups are tilted out of the image
plane by about ±15°.
(b) Superposition of the two QB positions, color-coded in
yellow, orange, and red, respectively, with the structures from
Stowell et al. (PDB entries 1aig and 1aij) of the same state and at the same pH,
shown in red. Hydrogen bonds to neighboring protein atoms are
indicated by broken green lines, with their length given in
Å.
(c) Schematic drawing of the QB movement. Distal
position in black, hypothetical intermediate position in green, and
proximal QB position in blue. Hydrogen bonds to the distal
position are color-coded orange, to the intermediate position in red,
and to the proximal QB position in magenta. The length of
the total QB movement and the
Cα–Cα distance are indicated
by arrows.
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