Fig. 4.

Identification of mitochondrial proteins and presequences. (A) Number of identified different proteins per million MS spectra. (B) Identification of presequence segments in proteins of the mitochondria-associated fraction. The sequences of the identified peptides found closest to the N terminus are shown. Numbers refer to amino acid positions, starting with the first residue of the presequences. The first and last residues of the mature proteins are indicated. Cytochrome b₂ is processed in two steps, after residues 31 and 80 (49).