Protein translocation pathways across the inner and outer mitochondrial membranes

Abstract

Mitochondria import different proteins that are encoded by nuclear genes and synthesized in the cytosol. Separate translocases in inner and outer mitochondrial membranes like TOM, TIM23, TOB/SAM, TIM22 complex facilitate recognition, import and intramitochondrial sorting of preproteins. Various cytosolic factors as Hsp70 and auxillary factors assist in targeting these preproteins to their destinations. Also, different protein components in the matrix participate in this energetically driven translocation process in a reaction that depends upon membrane potential and matrix-ATP. This review summarizes the present knowledge on import and sorting of mitochondrial precursor proteins with glance on unresolved questions.