RIBOSOMAL-PROTEINS NEIGHBORING 23-S RIBOSOMAL-RNA NUCLEOTIDES-803-811WITHIN THE 50-S SUBUNIT

We report the synthesis of a radioactive, photolabile oligodeoxyribonu cleotide probe and its exploitation in identifying 50 S ribosomal subu nit components neighboring its target site, nucleotides 803-811 in 23 S rRNA. Photolysis of the complex formed between the probe and 50 S su bunits leads to site-specific probe photoincorporation into proteins L 15, L17, and L20, labeled to greater extents, and L13 and L21, labeled to lesser extents. Portions of each of these proteins thus lie within 23 Angstrom of nucleotide U803, These results lead us to conclude tha t nucleotides 803-811 fall on the side of the L13-L17-L20-L21 protein cluster [Walleczek et al. (1988) EMBO J. 7, 3571-3576] that points fro m the back of the 50 S particle toward the peptidyl transferase center within the 50 S subunit. Such placement is consistent with the observ ation that an oligoDNA probe directed to nucleotides 803-811 decreases P-site binding of tRNA [Hill et al. (1990) Biochim. Biophys. Acta 105 0, 45-50].