Characterization and preliminary crystallographic studies on large ribosomal subunits from Thermus thermophilus

Diffracting crystals, suitable for X-ray crystallographic analysis, have been obtained from large (50 S) ribosomal subunits from Thermus thermophilus. These crystals, with P4 12 12 symmetry and a unit cell of 495 Å × 495 Å × 196 Å, reach typically a size of 0·15 mm × 0·25 mm × 0·35 mm. Using synchrotron radiation at cryo-temperature, these crystals diffract X-rays to better than 9 Å resolution, and do not show any measurable decay after a few days of irradiation. They complete a series of crystals, grown by us, from ribosomal particles of the same source, including a 30 S subunits, 70 S ribosomes and complexes of the latter with: (1) an oligomer of 35 uridine residues and (2) the same oligonucleotide together with approximately two Phe-tRNA Phe molecules. Crystallographic analysis of the various members of this series should provide information for investigating the conformational changes that take place upon the association of ribosomes from their subunits as well as upon binding of non-ribosomal components that participate in protein biosynthesis.