X-ray crystal structures of 70S ribosome functional complexes

Structures of 70S ribosome complexes containing messenger RNA and transfer RNA (tRNA), or tRNA analogs, have been solved by x-ray crystallography at u p to 7.8 angstrom resolution. Many details of the interactions between tRNA and the ribosome, and of the packing arrangements of ribosomal RNA (rRNA) helices in and between the ribosomal subunits, can be seen. Numerous contac ts are made between the 30S subunit and the P-tRNA anticodon stem-loop; in contrast, the anticodon region of A-tRNA is much more exposed. A complex ne twork of molecular interactions suggestive of a functional relay is centere d around the Long penultimate stem of 16S rRNA at the subunit interface, in cluding interactions involving the "switch" helix and decoding site of 16S rRNA, and RNA bridges from the 50S subunit.