title: Primary and secondary structure of rat 28 S ribosomal RNA.
abstract: The primary structure of rat (Rattus norvegicus) 28 S rRNA is determined inferred from the sequence of cloned rDNA fragments. The rat 28 S rRNA contains 4802 nucleotides and has an estimated relative molecular mass (Mr, Na-salt) of 1.66 X 10(6). Several regions of high sequence homology with S. cerevisiae 25 S rRNA are present. These regions can be folded in characteristic base-paired structures homologous to those proposed for Saccharomyces and E. coli. The excess of about 1400 nucleotides in the rat 28 S rRNA (as compared to Saccharomyces 25 S rRNA) is accounted for mainly by the presence of eight distinct G+C-rich segments of different length inserted within the regions of high sequence homology. The G+C content of the four insertions, containing more than 200 nucleotides, is in the range of 78 to 85 percent. All G+C-rich segments appear to form strongly base-paired structures. The two largest G+C-rich segments (about 760 and 560 nucleotides, respectively) are located near the 5'-end and in the middle of the 28 S rRNA molecule. These two segments can be folded into long base-paired structures, corresponding to the ones observed previously by electron microscopy of partly denatured 28 S rRNA molecules.
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004262:DNA Restriction Enzymes; D004275:DNA, Ribosomal; D005822:Genetic Vectors; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D012335:RNA, Ribosomal / Q000235:genetics*; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D004247:DNA; D004262:DNA Restriction Enzymes