Genetic and biochemical manipulations of the small ribosomal subunit from Thermus thermophilus HB8

Crystals of the small ribosomal subunit from Thermus thermophilus diffract to 3 Angstrom and exhibit reasonable isomorphism and moderate resistance to irradiation. A 5 Angstrom MIR map of this particle shows a similar shape t o the part assigned to this particle within the cryo-EM reconstructions of the whole ribosome and contains regions interpretable either as RNA chains or as protein motifs. To assist phasing at higher resolution we introduced recombinant methods aimed at extensive selenation for MAD phasing. We are f ocusing on several ribosomal proteins that can be quantitatively detached b y chemical means. These proteins can be modified and subsequently reconstit uted into depleted ribosomal cores. They also can be used for binding heavy atoms, by incorporating chemically reactive binding sites, such as -SH gro ups, into them. In parallel we are co-crystallizing the ribosomal particles with tailor made ligands, such as antibiotics or cDNA to which heavy-atoms have been attached or diffuse the latter compounds into already formed cry stals.