THE MITOCHONDRIAL PROTEIN IMPORT PATHWAY - ARE PRECURSORS IMPORTED THROUGH MEMBRANE CHANNELS

Mitochondrial biogenesis requires the import of hundreds of different proteins from the cytosol. Protein import into mitochondria is a multi step pathway that includes recognition of precursor proteins by machin ery both in the cytoplasm and on the mitochondrial surface, translocat ion of the precursor across one or both mitochondrial membranes, and f olding of the protein after its import into the organelle. Over the pa st several years, many components of the import machinery have been id entified using both biochemical and genetic methods. Recently, signifi cant progress has been made determining the function of some of these import proteins. One purpose of this minireview is to summarize our cu rrent understanding of the import pathway, and to introduce the topics of the minireviews that will follow. The other goal of this minirevie w is to discuss recent findings suggesting that proteins are transloca ted across both the mitochondrial inner and outer membranes through aq ueous channels.