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Figure 3.
Figure 3 The crystallographic structure of the ternary
complex (at 2.7 Å resolution) compared to the electron
microscopical reconstruction (18 Å resolution). a, The ternary
complex as revealed by X-ray crystallography10, with the
aminoacyl-tRNA shown in grey in the background in 'stick'
representation ('RASMOL'), and the EF-Tu in cartoon
representation in the foreground, rainbow colour-coded along the
length of the chain. The viewing direction is chosen to match
that of the ternary complex within the electron microscope
reconstruction shown in c. b, X-ray structure of the ternary
complex in space-fill representation ('IMAGIC'). c, Structure of
the ternary complex in the kirromycin-stalled
pre-translocational 70S ribosome extracted interactively from
the electron microscope 3D reconstruction. d, The X-ray and
electron microscopic densities superimposed. The X-ray structure
was aligned with respect to the electron microscopic
reconstruction mainly by the position of domain 2 of the EF-Tu.
Although the tRNA part of the ternary complex in the electron
microscopic reconstruction is simply a low-resolution version of
the X-ray structure, in the EF-Tu part of the complex some
differences exist with respect to the GTP-state X-ray structure
that cannot be accounted for by just the differences in
resolution between the structures.
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