IMPORT OF MITOCHONDRIAL CARRIERS MEDIATED BY ESSENTIAL PROTEINS OF THE INTERMEMBRANE SPACE

In order to reach the inner membrane of the mitochondrion, multispanni ng carrier proteins must cross the aqueous intermembrane space. Two es sential proteins of that space, Tim10p and Tim12p, were shown to media te import of multispanning carriers into the inner membrane. Both prot eins formed a complex with the inner membrane protein Tim22p. Tim10p r eadily dissociated from the complex and was required to transport carr ier precursors across the outer membrane; Tim12p was firmly bound to T im22p and mediated the insertion of carriers into the inner membrane. Neither protein was required for protein import into the other mitocho ndrial compartments. Both proteins may function as intermembrane space chaperones for the highly insoluble carrier proteins.