The enigmatic role of Mim1 in mitochondrial biogenesis

The translocase of the outer mitochondrial membrane (TOM complex) is a multi-subunit complex that serves as the general entry site for newly synthesized proteins into the organelle. The assembly of this complex is a multi-step process that requires the coordinated action of several proteins. A central, but rather undefined role in this process is played by Mim1, a mitochondrial outer membrane protein. The deletion of MIM1 leads to severe defects in the biogenesis of TOM complex subunits and to altered mitochondrial morphology. The protein is built from an N-terminal cytosolic domain, a central transmembrane segment, and a C-terminal domain facing the intermembrane space. In this review we summarize our current knowledge on the structure-function relationship of Mim1 and discuss some possibilities for its molecular function.