Interaction of amino acid-substituted partial extension peptides of adrenodoxin precursor with artificial membranes and isolated mitochondria.

The N-terminal fragment Met-Ala-Ala-Arg-Leu-Leu-Arg-Val-Ala-Ser-Ala-Ala-Leu-Gly (PA1-14) of the adrenodoxin precursor was previously found to inhibit the import of the precursor into mitochondria. In order to obtain further information on the structure-function relationship, five analogs of PA1-14 ([Leu1]PA1-14 (1), [Leu1,Ala10]PA1-14 (2), [Leu1,Ser4]PA1-14 (3), [Leu1,Arg11]PA1-14 (4) and [Leu1,Ser7,Arg10]PA1-14 (5) were synthesized. The CD study showed that PA1-14 and all analogs were random in an aqueous solution and formed an alpha-helical structure in the solution containing acidic liposomes. Peptides 1 and 2 were found to cause dye leakage from lipid vesicles more strongly than other analogs and PA1-14. All analogs completely inhibited the import of the precursor into mitochondria at a concentration of 30 microM. However, 1 and 2 destroyed the mitochondrial membrane potential. These results indicate that an increase in hydrophobicity by replacement of the Met and Ser residues by Leu and Ala, respectively, participates in the perturbation of the membranes. Furthermore, the requirement for the number and position of the Arg residue was found to be not very strict, although its presence in the extension peptide is essential for the precursor to import into mitochondria.