HOMOLOGOUS MATURASE-LIKE PROTEINS ARE ENCODED WITHIN THE GROUP-I INTRONS IN DIFFERENT MITOCHONDRIAL GENES SPECIFYING YARROWIA-LIPOLYTICA CYTOCHROME-C-OXIDASE SUBUNIT-3 AND SACCHAROMYCES-CEREVISIAE APOCYTOCHROME-B

A mitochondrial cox3 gene in the alkane yeast, Yarrowia lipolytica, encodes a subunit-3 protein of cytochrome c oxidase, and contains a 1044 base-pair-long intron, as compared with the corresponding intronless gene in Saccharomyces cerevisiae. The intron belongs to a group I intron as determined by the cDNA sequence for the splicing sites as well as the predicted RNA secondary structure. Remarkably, this intron could code for a protein of 206 amino-acid residues which showed 63% similarity with an RNA maturase encoded by the second intron of the mitochondrial apocytochrome b gene in S. cerevisiae. Both introns occurred within the conserved exon sequence, 5'-TT(G/C)AGGTGC-3', suggesting the possible transposition of a common ancestral intron.