Mitochondria-penetrating peptides: sequence effects and model cargo transport.

A class of mitochondria-penetrating peptides (MPPs) was studied in an effort to optimize their applications in the delivery of bioactive cargo to this therapeutically important organelle. The sequence requirements for mitochondrial entry were monitored, and it was discovered that while an alternating cationic/hydrophobic residue motif is not required, the inclusion of a stretch of adjacent cationic amino acids can impede access to the organelle. In addition, a variety of N- and C-terminal cargo were tested to determine if there are limitations to the lipophilicity, charge, or polarity of compounds that can be transported to mitochondria by MPPs. The results reported demonstrate that these peptide sequences are versatile transporters that will have a range of biological applications.