The Tom channel in the mitochondrial outer membrane: alive and kicking

The targeting of newly-made polypeptides to specific membranes, and the subsequent ability of a membrane to allow only certain polypeptides into its compartment, are essential to maintain the ultrastructure of Eukaryotic cells. Distinct oligomeric protein complexes in each cellular membrane catalyse these translocation processes. A recent report [Hill K et al. Nature 1998;395:516-521 (Ref. 1)] of the reconstitution of the translocation channel from the mitochondrial outer membrane, after producing the major structural component of the channel by recombinant means, promises a system to dissect in molecular detail the exact working of one of these protein translocation machines.