Mitochondrial N-Terminal Signal Sequences as Novel Antimicrobial and Annticancer Peptides

N-terminal mitochondrial targeting sequences (MTS) are signal peptides to drive the localization and import of mitochondrial protein and exhibit an amphipathic α-helix structure similar to that of almost all antimicrobial peptides (AMPs). Here, 2,939 mitochondrial proteins are excavated from various organisms, and 574 MTS are selected with an MTS possibility score exceeding 0.5, as determined via MitoFates (http://mitf.cbrc.jp/MitoFates/cgi-bin/top.cgi). 26 MTS composed of less than 20 amino acids is synthesized and analyzed their antimicrobial activities. The results showed that approximately 50% of MTS exhibited antimicrobial activity. Among them, human mitochondrial transcription termination factor 2 (hMTERF2-ts) is identified as an AMP candidate with strong antimicrobial activity against gram-positive and gram-negative bacteria, antibiotics-resistant (AR) bacteria, and fungi. Furthermore, it shows anticancer activities against various cancer cells, such as MDA-MB-231, HT-29, HepG2, and Panc-1 cells, with high stability against proteases, heat, pH, and salt, and low cytotoxicity toward normal cells, HaCaT and RAW 264.7. In addition, hMTERF2-ts effectively prevented the growth of Panc-1-implanted tumors without weight loss in BALB/c nude mice. In conclusion, this study suggests that MTSs of protozoa are powerful and novel AMP candidates with low cytotoxicity against normal cells.