Details

Autor(en) / Beteiligte

• KOP, JOANN LAI WAH

Titel

PRIMARY AND SECONDARY STRUCTURES OF BACILLUS RIBOSOMAL-RNAS

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

1982

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The secondary structure of ribosomal RNAs has been a difficult problem to probe due to the inherent complexity of the ribosome. Physical chemistry and biochemistry techniques have resulted in structures of low resolution. Therefore, a comparative approach to rRNA secondary structure was attempted. This comparative approach is based on the assumptions that all ribosomes evolved from the same common ancestral molecule and that changes in these molecules have been severely constrained by function. A partial sequence for the B. brevis 16S rRNA has been determined. Partial digests, using RNase T(,1), pancreatic RNase, and cobra venom RNase, were used to generate fragments whose sequences were determined by the Sanger or Peattie methods of RNA sequencing. The sequence was then used in a comparative analysis with the E. coli 16S rRNA sequence (from the rrnB operon). The resulting secondary structure was described by Woese et al. (Nucleic Acids Research 8:2275, 1980). This model is consistent with the nuclease cleavage sites and bisulfite modification data from B. brevis studies. A 23S rRNA gene from B. stearothermophilus was cloned and its sequence determined by the Maxam and Gilbert DNA sequencing method. The 23S rRNA was found to be 2929 nucleotides in length. When compared to the E. coli 23S rRNA gene sequence from the rrnB operon, the secondary structure proposed by Noller et al. (Nucleic Acids Research 9:6167, 1981) emerged. Free energy values for the various helices in E. coli and B. stearothermophilus were calculated and compared to probe for differences between rRNAs from thermophilic and mesophilic organisms. It was found that approximately half of the B. stearothermophilus helices have a free energy greater than that of E. coli. In addition, B. stearothermophilus has a slightly higher G+C content and G-C base pair content, fewer G-U base pairs and in general, fewer irregularities in secondary structure. All these factors may contribute a small part to the increased stability of the rRNA in a thermophilic environment. In general, the comparative analysis has produced secondary structures for 16S and 23S rRNAs which can be accommodated by rRNA sequences from a variety of organisms.