STRUCTURAL REQUIREMENT FOR RECOGNITION OF THE PRECURSOR PROTEINS BY THE MITOCHONDRIAL PROCESSING PEPTIDASE

We examined the structural characteristics of the extension peptides r esponsible for the recognition by the mitochondrial processing peptida se by using pre-adrenodoxin, which has a long extension peptide of 58 amino acid residues, as the substrate. The deletion of various parts o f the extension peptide of pre-adrenodoxin indicated that more than 40 amino acid residues and the presence of basic amino acid residues in the distal portion (20-40 amino acid residues upstream of the cleavage site) were necessary for the recognition of the precursor by the pept idase. The processing of pre-adrenodoxin was strongly inhibited by the synthetic peptide corresponding to the middle portion of the extensio n peptide, whereas the peptide corresponding to the amino-terminal por tion exhibited weak inhibition of the processing. The replacement of a rginine residues in the middle portion of the extension peptide with n eutral amino acids resulted in a great decrease in the processing. We conclude that basic amino acids at a position distal to the cleavage s ite are necessary for the recognition of the precursor proteins by the processing peptidase and that basic amino acids required for the mito chondrial targeting and those for the recognition by the peptidase are separately located in the extension peptide of pre adrenodoxin.