Figure 4.
Fig. 4. (A) Electron density (2Fo-Fc) contoured at 1.5 (blue) for the
two-histidine region and surrounding structure, including
conserved Asp160 that accepts four short hydrogen bonds (dashed
yellow). Additional peaks Am2, Am3, and Am4 seen when
crystallized with 25 mM ammonium sulfate are defined in the
Fo-Fc omit map at 1.5 (in red),
indicating putative NH[3] molecule positions (blue spheres). The
hydrogen-bonding network shows interactions between His168 and
His318 and NH[3] peaks in yellow (distances in red). (B) Stereo
view of the two-histidine center of the channel. Surrounding
hydrophobic residues are shown in ball and stick representation.
The surface representation covers other surrounding amino acids.
Three ammonia-dependent sites are shown (blue spheres) with
associated distances (dashed yellow line and yellow labels).
The above figure is reprinted
by permission from the AAAs:
Science
(2004,
305,
1587-1594)
copyright 2004.
(blue) for the
two-histidine region and surrounding structure, including
conserved Asp160 that accepts four short hydrogen bonds (dashed
yellow). Additional peaks Am2, Am3, and Am4 seen when
crystallized with 25 mM ammonium sulfate are defined in the
Fo-Fc omit map at 1.5