Euglena gracilis chloroplast ribosomal RNA transcription units. II. Nucleotide sequence homology between the 16 S-23 S ribosomal RNA spacer and the 16 S ribosomal RNA leader regions

• Published in: The Journal of biological chemistry 1980-11, Vol.255 (22), p.10997-11003
• Main Authors: Orozco, E.M. Jr, Rushlow, K.E, Dodd, J.R, Hallick, R.B
• Format: Article
• Language: English
• Subjects: Algae; Base Sequence; Chloroplasts - metabolism; DNA - metabolism; DNA Restriction Enzymes; Euglena gracilis - metabolism; Molecular Weight; Nucleic Acid Conformation; RNA, Ribosomal - biosynthesis; RNA, Transfer - biosynthesis; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)70406-2

The DNA sequences of two segments of the ribosomal RNA transcription units of Euglena gracilis Pringsheim strain Z chloroplast DNA have been determined. The first is from the 16 S to 23 S rRNA spacer region. The nucleotide sequence determined includes 64 bp from the 3'-end of the 16 S rRNA gene, the adjacent 87-bp spacer containing 68A-T base pairs, a tRNAIle gene, a 9-bp spacer, a tRNAAla gene, a spacer of approximately 15 bp, and the first 120 bp from the 5'-end of the 23 S rRNA gene. The gene organization of the 16 S to 23 S rRNA spacer, the identity of the tRNA genes, and the tRNA anticodons for the E. gracilis rRNA transcription units are identical with that of the rrnA, D, and X operons of Escherichia coli. The second DNA segment which was sequenced is from a region preceding the 5'-end of the 16 S rRNA gene. Within a continuous region of 189 bp in this 16 S rRNA leader sequence, 68% of the bases are homologous to the 16 S rRNA to 23 S rRNA spacer region. This homology includes the 3'-end of the 16 S rRNA gene, the adjacent spacer, and a complete "pseudo" tRNAIle gene. This leader sequence which has the same polarity as the rRNA transcripts, is flanked by nucleotide sequences resembling partial tRNA genes.