Methylated regions of hamster mitochondrial ribosomal RNA: structural and functional correlates

The positions of post-transcriptionally methylated residues within hamster mitochondrial ribosomal RNA have been established. Comparisons with other mitochondrial rRNA, and with bacterial, eucaryotic and chloroplast rRNA show that the methylated regions i) are comprised of conserved primary sequences and/or secondary structures and ii) are situated at the subunit interface of the ribosome. The comparative analyses also reveal that the ribose-methylated sequence UmGmU of hamster mitochondrial large ribosomal subunit (LSU1) RNA lies in a universally conserved hairpin loop which contains a putative puromycin-reactive nucleotide. The "UmGmU hairpin" is within 100 nucleotides of two chloramphenicol-resistance residues of LSU RNA. We present a secondary structure for this region which is conserved in LSU RNAs. This structure allows physical juxtaposition of the three antibiotic-interacting loci and thus defines RNA components of the ribosomal-binding site for the 3'-terminus of aminoacyl-tRNA.