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Figure 1.
FIGURE 1. A, ribbon diagram of pig GTP-specific SCS showing
the location of the GTP-binding site. The  -subunit is green, the
 -subunit is yellow,
except for the T-loop, which is highlighted in magenta. GTP, the
potassium ion, and the side chain of the phosphorylated
histidine residue, His-259 , are drawn as stick
models and colored according to atom type: red for oxygen,
yellow for carbon, blue for nitrogen, green for phosphorus, and
turquoise for potassium. B, stereo view of the electron density
for GTP and the potassium ion, including nearby residues of the
ATP-grasp domain of pig GTP-specific SCS. The F[o] - F[c], [c]
electron density map calculated without GTP and the potassium
ion is contoured at 3  . C, stereo view of the
electron density for GDP and the potassium ion, including nearby
residues of the ATP-grasp domain of pig GTP-specific SCS. The
F[o] - F[c], [c] electron density
map calculated without GDP and the potassium ion is contoured at
3 .
The same atom colors were used in B and C as described for A.
All parts of the figure were drawn using the program RASTER3D
(58), and B and C also used the program XFIT (47).
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