DNA duplication has resulted in transfer of an amino-terminal peptide between two mitochondrial proteins

Abstract

The mitochondrial genome of the ascomycete Aspergillus nidulans possesses at least nine unidentified reading frames (URFs). Two of these are particularly interesting in that the amino acid sequences of the derived translation products are very similar in the N-terminal regions. The first 36 residues of the URFx gene product are repeated at the start of a second reading frame, URFA3, with only six mismatches. Despite this similarity in their amino-termini, the latter parts of URFx and URFA3 are completely different. Closer examination of the nucleotide sequences at the 5' ends of the two genes shows that the conserved peptides are part of a 300-base pair (bp) duplication within the mitochondrial genome. This duplication also includes the tRNA gene for asparagine and a conserved 116-bp intergenic region.