Cytochrome b, the var 1 protein, and subunits I and III of cytochrome c oxidase are synthesized without transient presequences in Saccharomyces cerevisiae.

The N-termini of four mitochondrial translation products, the var 1 protein, cytochrome b, and subunits I and III of cytochrome c oxidase have been characterized in Saccharomyces cerevisiae and compared with the known DNA sequences of the respective structural genes. The four mature proteins correspond to the predicted primary translation products and retain the formylated methionine residue. Thus, subunit II of cytochrome c oxidase studied previously [Pratje et al. (1983) EMBO J.2, 1049-1054] is so far the only mitochondrial translation product carrying a N-terminal-extended transient presequence in S. cerevisiae.