THE MIM COMPLEX MEDIATES PREPROTEIN TRANSLOCATION ACROSS THE MITOCHONDRIAL INNER MEMBRANE AND COUPLES IT TO THE MT-HSP70 ATP DRIVING SYSTEM/

We have identified a complex in mitochondria that functions as a part of the preprotein import machinery of the inner membrane (MIM complex) . Two known components, MIM23 and MIM17, and two novel components, MIM 33 and MIM14, were found as constituents of this complex. In the prese nce of a translocating chain, the outer membrane import machinery (MOM complex) and the MINI complex form translocation contact sites. On th e matrix side, the MIM complex is associated with the mt-Hsp70-MIM44 s ystem. We propose a structure of the import machinery in which the MIM complex constitutes a proteinaceous channel that accepts preproteins from the MOM complex, facilitates their reversible transmembrane movem ent, and mediates unidirectional transport by linkage to the ATP-depen dent mt-Hsp70-MIM44 system.