The majority of proteins targeted to mitochondria have a presequence that direct translocation across the outer and inner mitochondrial membranes. The Translocase of the Outer mitochondrial Membrane (TOM complex) is a large multimeric machine, that is regulated by kinases and chaperones located in the cytosol. The majority of nuclear-encoded proteins are imported via the TOM channel. Beta-barrel proteins of the outer membrane are inserted via the SAM (Sorting and Assembly Machinery) complex. In addition, the SAM complex can engage with two outer membrane proteins: Mdm10 and Mim1. Mim1 functions in assembly of the multimeric TOM complex. Mim1 and Mdm10 are each required for integration of different subunits into the TOM complex.

In this work we are using mitochondrial in vitro import assays of radio-labeled precursors in order to study the role that the TOM complex, Mim1, as well as cytosolic chaperones play in the import and insertion of alpha helical proteins into mitochondrial outer membrane.