Which targeting signal is required for protein import into the mitochondria?
Majority of mitochondrial proteins are encoded by nuclear genome synthesized in cytosol as precursors requiring active import. Matrix targeting signal resides typically at extreme N-terminus forming 15 to 70 amino acid extension lacking acidic residues and capable of adopting amphipathic alpha-helical conformation with positively charged lysine and arginine residues clustered on one face creating basic patch and hydrophobic leucine, phenylalanine on opposite face. This structure is recognized by receptor domains of translocase of outer membrane Tom20 with hydrophobic groove plus Tom22 acidic d
Ref: Neupert & Herrmann, Annu Rev Biochem 2007, Mitochondrial Protein Import. Alberts 7th ed., Chapter 12.
