|
Figure 3.
FIG. 3. The metal centers. A, the F[o] - F[c] electron
density maps of the native enzyme in complex with 100 mM ZnCl[2]
contoured at 15  level and shown in
magenta, with 50 mM CdCl[2] contoured at 15 level and shown in
cyan, and with 100 mM CuCl[2] contoured at 18 level
and shown in green. The metal ligands are shown as a
ball-and-stick representation, with the Zn2+ and Cu2+ ions as
magenta and green spheres, respectively. Zn2+ and Cd^2+ bind at
the  subsite, where Cu2+
binds at the [2] subsite. B, the
2F[o] - F[c] electron density maps of the H220A mutant contoured
at 2.5 level and shown in
cyan, and the difference map for the zinc ion contoured at 15
level and shown in
magenta. The endogenous zinc ion binds at the [3]
subsite instead of the  site in this mutant. C,
the 2F[o] - F[c] electron density map of the D366A mutant
contoured at 2.5 level and shown in
cyan, and the difference map for the zinc ion in complex with
100 mM ZnCl[2] contoured at 15 level and shown in
magenta. The additional zinc ion binds at the [4]
subsite. D, superposition of the native enzyme with 100 mM
ZnCl[2] in blue, the native enzyme with 100 CuCl[2] in green,
the H220A mutant in yellow, and the D366A mutant with 100 mM
ZnCl[2] in red. The different metal coordination is carried out
by small shifts in the side chains of ligands and small
movements of the metal ions.
|
