Translation of the edited mRNA for cytochrome b in trypanosome mitochondria

The type of RNA editing found in the kinetoplast-mitochondria of trypanosomes and related protozoa, involving uridylate insertions and deletions, creates translatable messenger RNAs (mRNAs) out of nonsense pre-edited RNAs by correcting encoded defects that vary from simple frameshifts to large "cryptic" regions. However, any evidence for translation of these mRNAs in the kinetoplast has been missing for decades. We identified a kinetoplast-encoded protein, apocytochrome b, whose mRNA is edited in the 5' region. The determined amino-terminal sequence of the protein coincides with the predicted sequence derived from the edited region, demonstrating that the cognate apocytochrome b mRNA is translated into a functional protein. This finding represents the first direct evidence for a functional translation system in the kinetoplasts.