Protein translocation pathways of the mitochondrion

The biogenesis of mitochondria depends on the coordinated import of precurs or proteins from the cytosol coupled with the export of mitochondrially cod ed proteins from the matrix to the inner membrane. The mitochondria contain an elaborate network of protein translocases in the outer and inner membra ne along with a battery of chaperones and processing enzymes in the matrix and intermembrane space to mediate protein translocation, A mitochondrial p rotein, often with an amino-terminal targeting sequence, is escorted throug h the cytosol by chaperones to the TOM complex (translocase of the outer me mbrane), After crossing the outer membrane, the import pathway diverges; ho wever, one of two TIM complexes (translocase of inner membrane) is generall y utilized. This review is focused on the later stages of protein import af ter the outer membrane has been crossed. An accompanying paper by Lithgow r eviews the early stages of protein translocation, (C) 2000 Federation of Eu ropean Biochemical Societies. Published by Elsevier Science B,V. All rights reserved.