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Ribosomal RNA operons in Streptococcus pneumoniae: Gene organization and copy number

Ribosomes and transfer ribonucleic acids (tRNAs) are integral parts in the cells protein synthesis machinery. tRNAs are small polymers of ca. 77 RNA residues in length. The ribosome is a ribonucleo-protein, a large heterologous complex comprised of ca. 55 proteins and three species of ribosomal RNAs (rRNA). The ribosomal RNAs (and quite often the tRNAs) are organized on the chromosome in a close linear array known as the rRNA operons. The organization of these genes into multi-gene clusters ultimately facilitates the cell's regulation of the protein synthesis apparatus. / Isoleucine and alanine tRNAs are encoded tandemly within the 16S-23S intergenic spacer of some eubacterial rRNA operons. A previous study has demonstrated that the intergenic spacer in the eubacterium S. pneumoniae is unconventional. The isoleucine tRNA is not tandemly encoded with the alanine tRNA. Rather it appears to be encoded at the distal end of the operon near the 5S rRNA gene. This unique organization, the presence of numerous direct repeats in the non-coding regions of the 16S-23S intergenic spacer, and the potential for stem-loop formation of the isoleucine tRNA gene suggest that it might have been rearranged intrachromosomally via an illegitimate recombination. / Reported herein is a characterization of the distal spacer regions of the rRNA operons on the S. pneumoniae chromosome. Dot-blot hybridization analysis shows that the number of 16S rRNA genes on the S. pneumoniae chromosome is four. This is consistent with a previous study wherein the results suggested a minimum copy number of four for the rRNA operons. The distal spacer region from each of the four ribosomal RNA operons has been cloned and sequenced. An isoleucine tRNA is encoded on two of the four cloned fragments. DNA sequence analysis of the regions flanking the cloned isoleucine tRNA genes revealed motifs that are consistent with one of the popular models for illegitimate recombination. / Source: Dissertation Abstracts International, Volume: 53-11, Section: B, page: 5529. / Major Professor: Robert Hunter Reeves. / Thesis (Ph.D.)--The Florida State University, 1992.
ContributorsBacot, Christopher Matthew., Florida State University
Source SetsFlorida State University
Detected LanguageEnglish
Format91 p.
RightsOn campus use only.
RelationDissertation Abstracts International

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