The nucleotide sequence of a segment of Trypanosoma brucei mitochondrial maxi-circle DNA that contains the gene for apocytochrome b and some unusual unassigned reading frames

Abstract

The nucleotide sequence of a 2.5-kb segment of the maxi-circle of Trypanosoma brucei mtDNA has been determined. The segment contains the gene for apocytochrome b, which displays about 25% homology at the amino acid level to the apocytochrome b gene from fungal and mammalian mtDNAs. Northern blot and S1 nuclease analyses have yielded accurate map positions of an RNA species in an area that coincides with the reading frame. The segment also contains two pairs of overlapping unassigned reading frames, which lack homology with any known mitochondrial gene or URF. The DNA sequence in these areas is AG-rich (70%), resulting in URFs with an unusually high level of glycine and charged amino acids (60%). They may not encode proteins, in spite of their size and the fact that abundant transcripts are mapped in these areas.