The mitochondrial protein import apparatus.

INTRODUCTION ..................................................................................... 331 THE PRECURSOR PROTEINS .................................................................... 332 Targeting Signals ................................................................................. 332 Translocation Competence ...................................................................... 335 IMPORT ECEPTORS .............................................................................. 337 MEMBRANE INSERTION OF PRECURSOR P OTEINS .................................. 340 A General Insertion Protein .................................................................... 340 Pathway of Apocytochrome c ................................................................... 342 Partial and Artificial Systems .................................................................. 342 TRANSLOCATION CONTACT SI ES .......................................................... 343 COVALENT AND NONCOVALENT MODIFICATION OF IMPORTED PRECURSOR PROTEINS ............................................................... 345 Processing Enzymes .............................................................................. 345 A Folding Machinery ............................................................................ 346 INTRAMITOCHONDRIAL SO TING ........................................................... 348 Conservative Sorting ............................................................................. 348 Nonconservative Sorting ......................................................................... 349 SUMMARY ND PERSPECTIVES .............................................................. 350