Intron Within the Large RRNA Gene of N. Crassa Mitochondria: a Long Open Reading Frame and a Consensus Sequence Possibly Important in Splicing

We describe the sequence of the 2295 nucleotide long intron and 245 nucleotides of the flanking exon sequences within the large (24S) rRNA gene of Neurospora crassa mitochondria. The intron contains a long open reading frame, which could correspond to ribosomal protein S5. Comparison with the corresponding intron of the large rRNA gene of yeast mitochondria reveals a single highly homologous 57 nucleotide long sequence, including the sequence (formula; see text), which is present in virtually all the sequenced introns of yeast, Aspergillus nidulans and Zea mays mitochondrial genes, and which may be important for their processing. Sequences closely related to this consensus sequence are also present within all four of the introns of nuclear rRNA genes which have been sequenced. The intron is located within a highly conserved region of the large rRNA sequence and at exactly the same site as in the corresponding introns in yeast mitochondria and also in Physarum polycephalum nuclei.