|
Figure 6.
Figure 6. Coupling of the conformational change of the GAC with
the movement of aa-tRNA. (a) Comparison of the aa-tRNA
position defined inside the cryo-EM density for the ternary
complex (green) versus the position of the aa-tRNA in the atomic
coordinates of Phe-tRNA^Phe -EF-Tu -GDPNP -kir (gray). The
ribbons representation of the GAC and the SRL serves as a frame
of reference to make it apparent that the change in the aa-tRNA
position follows the conformational change of the GAC while the
aa-tRNA maintains its position in the region of the SRL. The GAC
position shown correspond to the fitting of the atomic
coordinates in the 'closed' GAC from the 70S -fMet-tRNA^fMet
-Phe-tRNA^Phe -EF-Tu -GDP -kir complex. The ribosomal
orientation is depicted in the thumbnail. (b -d) The postulated
coupling between the movement of the GAC and the approach of the
aa-tRNA to LH69. In a hypothetical initial binding, the 'open'
GAC would interact with the aa-tRNA delivered in the ternary
complex by EF-Tu (b). The transition of the GAC to the closed
conformation (c) brings the aa-tRNA in contact with LH69. The
aa-tRNA -LH69 interaction facilitates a distortion in the
aa-tRNA (d) that reorients the anticodon arm (in the region
encircled) and allows a codon (cd)-anticodon recognition.
|
