Figure 3. From the single macromolecule to its integration in supramolecular biological systems: the example of transfer RNAs.

(Left) SAXS curve from which a boomerang-shaped model of tRNA was deduced (Witz, 1964; Witz, 2003) and a balsawood model built after the X-ray analysis of yeast tRNA^Asp at 3 Å resolution (Moras et al., 1980). (Middle) first X-ray structures of tRNAs in complex with proteins from the translation machinery: E. coli tRNA^Gln in interaction with monomeric class Ib GlnRS (in green) (Rould et al., 1989), S. cerevisiae tRNA^Asp in interaction with its cognate dimeric class IIb AspRS (in blue) (Ruff et al., 1991), and phenylalanyl-tRNA^Phe in interaction with bacterial elongation factor EF-Tu (in pink) (Nissen et al., 1995). (Right) view of the E. coli ribosome in translation with the three tRNA molecules bound to A, P, and E sites obtained by fitting an atomic model (derived from X-ray structures) in a 6.7 Å resolution cryo-EM map (Villa et al., 2009). Ribosomal proteins from 30 S and 50 S subunits are shown in yellow and blue, respectively, and 23 S, 5 S, and 16 S RNAs in dark, medium, and light green, respectively. The mRNA is symbolized by a violet ribbon and the tRNA in the A site is bound to EF-Tu (pink). Models in the middle and on the right are shown at the same scale.