Abstract: 5.5 Angstrom resolution x-ray crystallographic structures of 70S ribosome complexes containing messenger RNA and tranfer RNA (tRNA), or tRNA analogs, are provided. The resolution has been enhanced by fitting atomic resolution structures of 30S and 50S subunits onto the 5.5 anstrong electron density map. The enhanced structure reveals regions of structural differences between the 70S complex and the structures of the individual 30S and 50S components. Pharmacophore design to discover novel inhibitors or activators may be carried out using the enhanced 5.5 Angstrom 70S structure.

Abstract: Structures of 70S ribosome complexes containing messenger RNA and transfer RNA (tRNA), or tRNA analogs, have been solved by x-ray crystallography at up to 5.5 Angstrom resolution. Many details of the interactions between tRNA and the ribosome, and of the packing arrangement of ribosomal RNA (rRNA) helices in and between the ribosomal subunits can be seen. Numerous contacts 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 network of molecular interactions suggestive of a functional relay is centered around the long penultimate stem of 16S rRNA at the subunit interface, including interactions involving the “switch” helix and decoding site of 16S rRNA and RNA bridges from the 50S subunit. We have enhanced the resolution our 5.5 Angstrom resolution map by fitting atomic resolution structures of 30S and 50S subunits onto our 5.5 Angstrom electron density map.