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Figure 1.
Figure 1. The KMgATP binding site and a model for ATP
hydrolysis. (A) An electron density map is contoured at 4s
(green) and 6s (magenta) in the s[A]-weighted residual F[o]
-F[c] map using the final model with all coordinated water
molecules removed. Coordination bonds to metal ions are shown in
green, coordination polyhedron in silver, and hydrogen bonds in
red dashes. Coordination bond lengths calculated from all 14
subunits for Mg to O2a, O1b, O3g, W555, W556, and D87 are
2.24(±0.07), 2.32(±0.10), 2.21(±0.08),
2.27(±0.14), 2.10(±0.11), and 2.33(±0.05)
Å, respectively. The coordination bond lengths for K to
O1a, W551, W552, W553, W554, T30, and K51 are
2.55(±0.05), 2.50(±0.06), 2.78(±0.06),
2.60(±0.10), 2.59(±0.09), 2.59(±0.05), and
2.53(±0.08) Å, respectively. (B) A hypothetical
attacking hydroxyl ("W999") for ATP hydrolysis is placed on the
line connecting D52 to the gP atom at a distance of 2.8 Å to D52.
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