Protein Import into Mitochondria

Mitochondrial biogenesis relies on the transport of hundreds of different precursor proteins from the cytosol into the different mitochondrial subcompartments. Proteins destined to the mitochondrial matrix contain aminoterminal matrix targeting sequences, also called presequences, which are recognized by cytosol-exposed receptors on the mitochondrial outer membrane. Translocation complexes in the outer membrane, the TOM complex, and in the inner membrane, the TIM23 complex, then thread these precursor proteins into the matrix, where the presequences are often removed by the matrix processing peptidase. Proteins of the outer membrane, the intermembrane space, and the inner membrane can contain internal targeting signals which allow them to embark on specific sorting routes to reach their final location.