A 28 kDa mitochondrial protein is radiolabelled by crosslinking with a 123I-labelled presequence

Abstract A 13-residue peptide containing the first 12 amino acids of the N-terminal part of the signal sequence of yeast cytochrome ???oxidase subunit IV is shown by chemical crosslinking to interact with a mitochondrial protein. This result is obtained with mitochondria from four different origins. Submitochondrial localization experiments suggest that the 28 kDa labelled component is present on the outer face of the inner membrane. Since such addressing peptides are imported into mitochondria through the same machinery as protein precursors, the 28 kDa protein might be a component of the translocation apparatus.