Nucleotide Sequences from Specific Areas of the 16S and 23S Ribosomal RNAs of <i>E. coli</i>

Abstract

The primary structures of the 16S and 23S ribosomal RNAs of Escherichia coli have been studied. Nucleotide sequences have been determined which occur in specific areas close to the small numbers of methylated nucleotides which are present in these molecules. Fragments containing these methylated nucleotides were obtained by digestion of radioactive RNA substrates with T 1 ribonuclease. Such digestion products were fractionated by high‐voltage electrophoresis in two dimensions. The 23S RNA yielded predominantly 11 methylated oligonucleotides on digestion, and the 16S RNA gave rise to 6 methylated components. Nucleotide sequence analysis of these products was carried out, and the nature of the modified nucleotides occurring in each product was also examined. It was found that some of the sequences contained several modified components positioned close to each other. Quantitative studies indicate that each of the methylated sequences is probably present twice in a molecule of the 23S RNA, so that these sequences encompass about 5% of the nucleotides present in the entire molecule. It is postulated that extensive repetition of nucleotide sequences occurs within the 23S RNA.