title: The sequence of the gene for cytochrome c oxidase subunit I, a frameshift containing gene for cytochrome c oxidase subunit II and seven unassigned reading frames in Trypanosoma brucei mitochondrial maxi-circle DNA.
abstract: A 9.2 kb segment of the maxi-circle of Trypanosoma brucei mitochondrial DNA contains the genes for cytochrome c oxidase subunits I and II (coxI and coxII) and seven Unassigned Reading Frames ("URFs"). The genes for coxI and coxII display considerable homology at the aminoacid level (38 and 25%, respectively) to the corresponding genes in fungal and mammalian mtDNA, the only striking point of divergence being an unusually high cysteine content (about 4.5%). The reading frame coding for cytochrome c oxidase subunit II is discontinuous: the C-terminal portion of about 40 aminoacids, is present in the DNA-sequence in a -1 reading frame with respect to the N-terminal moiety. URF5, 8 and 10, show a low but distinct homology (about 20%) to mammalian mitochondrial URF-1, 4 and 5, respectively. In URF5, the first AUG is found at codon 145, whereas extensive homology to mammalian URF-1 sequences occurs upstream of this position. The possibility exists that UUG can serve as an initiator codon. URF7 and URF9 have a highly unusual aminoacid composition and do not possess AUG or UUG initiator codons. These URFs probably do not have a protein-coding function. The segment does not contain conventional tRNA genes.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000235:genetics*; D005796:Genes; D005815:Genetic Code; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics; D014346:Trypanosoma brucei brucei / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D046911:Macromolecular Substances; D012333:RNA, Messenger; D012343:RNA, Transfer; D003576:Electron Transport Complex IV