|
Figure 5.
FIG. 5. Refined structure of the human E1b active site at
the interface between  - and  '-subunits. 2F[o] - F[c]
electron densities (in green) are contoured at 1  . Only
two histidine residues are within 5-Å distance from the C2
atom of the bound ThDP. His146- is hydrogenbonded to the
O4 water molecular, whereas His291- forms hydrogen bonds to
the O1 and O2 water molecules (in red spheres); the former in
turn coordinates to the terminal phosphate oxygen of ThDP. The
channel leading to the activated C2 atom of ThDP lies at the
interface between the - and '-subunits, such that
these two histidine residues flank opposite sides of the
channel. A Mn2+ ion is bound at the metal ion binding site in
place of the common Mg2+ ion. Good electron density is present
for Ser292- (phosphorylation site
1), which is positioned at the opening of the channel. Carbon
atoms are in gold, ThDP in green, oxygen atoms in red, nitrogen
atoms in blue, phosphorous atoms in magenta, and sulfur atoms in
yellow. Graphics were generated with the programs BobScript (24)
and PovRay (Persistence of Vision, v3.02, POV-Team,
www.povray.org).
|
