title: Toxoplasma gondii: structure and characterization of the 26S ribosomal RNA and peptidyl transferase domain.
abstract: The 26S, 5.8S, and the intergenic spacer ribosomal DNAs (rDNA) of Toxoplasma gondii have been cloned and completely sequenced from both DNA strands. The length of the large subunit was found to be 3487 nucleotides and the 5.8S was 153 nucleotides long. These formed the large rRNA subunit of Toxoplasma and were mapped in the rDNA unit known to be repeated 110 times in a head-to-tail fashion in the genome. Primer extension analysis and multiple alignments localized the 5' end point of the two rRNAs. Comparisons with Toxoplasma rDNA by nucleic acid homology studies gave 76% similarity with the dinoflagellate Prorocentrum micans, 66% with yeast Saccharomyces cerevisiae, and 64% with the ciliate Tetrahymena thermophila. Similarity was apparent in the conserved core structure of the large subunit rRNA and divergent sequences were identified in the so-called divergent domains. Construction of a secondary structure model of the peptidyl transferase center of the large rRNA revealed similarities with the same domain from other life forms.
authors.affiliation: Pavillon Charles-Eugène Marchand et Faculté de Médecine, Université Laval, Ste-Foy, Québec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Gagnon
authors.forename: M J
authors.initials: MJ
authors.lastname: Morency
authors.forename: D
authors.initials: D
authors.lastname: Bourbeau
authors.forename: R C
authors.initials: RC
authors.lastname: Levesque
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010458:Peptidyl Transferases; D012335:RNA, Ribosomal / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014122:Toxoplasma / Q000201:enzymology / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; C065096:RNA, ribosomal, 26S; D010458:Peptidyl Transferases